Merkuri
Explorer
This looks great! Part of my job at work is to be a quality assurance tester, and I often work with people for whom English is a second language, so I'm used to correcting improper English, making suggestions, and finding bugs. So please interpret this list of criticisms as constructive. 
If it matters, I'm using Chrome.
Suggestions:
This:
Should be (IMO):
In the "Events" box you can probably change the sub-header to "Events you are attending" (the "all" is a little redundant) and the Friends box probably doesn't need a sub-header at all.
I feel that things in all caps should be used sparingly, so things like "ADD A FRIEND" or "EDIT YOUR PROFILE" can probably be capitalized, but they shouldn't be in all caps ("Add a Friend" and "Edit Your Profile"). The exception is if they're in some sort of a graphic button or in a funky font.
The "Your location" item in the key can probably just be replaced with "You" but it's not bad as it is now. It might be nice if "Your location" was a different color, too. I understand that I'm a member, which is why I'm green, but it would be a lot easier to pick out your own location if it was a different color. It doesn't stand out as much when it's the same color as other things on the map, just with an asterisk on it.
After picking your location on the map it should probably give you a link to go back to the main GsG page instead of to the forums.
When creating a new event if the user has no social groups the dropdown should be filled with something like, "(you are not a member of any groups)" instead of just being empty. Empty dropdowns look bad.
When searching on the main page it was not immediately apparent to me that it had worked. The search area dropdown reverted to 100 and I didn't see anything new on the map. It took me a while to realize that the search results were below the map. You might want to either put the results above the map or include a little bit of text above the map that says something like "Found X members, Y groups, and Z events. Jump to results" with a clickable link to jump down to the results.
If you click on a user's profile, then hit the back button, it should have your map zoomed into the same spot. Right now it seems to reset back to your "home" location.
Bugs/problems:
I think someone else mentioned this already, but when I go to add a new event I see this at the top of the screen:
When you click on a user or event on the map the name shows up in yellow text on white. Extremely hard to read unless you mouse-over it.
Question:
My brain often has a problem wrapping itself around time zone changes and DST changes, so I don't know if this is just me, but I find "Maintain same time throughout the year, regardless of DST changes" a little hard to understand. Does that mean that if I pick 5 PM Eastern and check that box that the game will always be 5 PM Eastern, regardless of whether we're in DST or not? And if the box was unchecked then when DST changes it'll be shifted an hour (to 4 PM or 6 PM, depending on which change happened)? It might be nice to include a little example in there for people like me who are time-zone challenged.
Is there a way to type in an address to set your location, instead of picking it from the map? If not, this would be nice to have. At the very least it would be nice to type in a location and get the map to center there, then you can zoom in and click the screen to set the location.

If it matters, I'm using Chrome.
Suggestions:
This:
Welcome, Merkuri. You did not set a location yet, so the location is taken from the IP.
Should be (IMO):
Welcome, Merkuri. You did not set your location yet, so your location has been determined from your IP address.
In the "Events" box you can probably change the sub-header to "Events you are attending" (the "all" is a little redundant) and the Friends box probably doesn't need a sub-header at all.
I feel that things in all caps should be used sparingly, so things like "ADD A FRIEND" or "EDIT YOUR PROFILE" can probably be capitalized, but they shouldn't be in all caps ("Add a Friend" and "Edit Your Profile"). The exception is if they're in some sort of a graphic button or in a funky font.
The "Your location" item in the key can probably just be replaced with "You" but it's not bad as it is now. It might be nice if "Your location" was a different color, too. I understand that I'm a member, which is why I'm green, but it would be a lot easier to pick out your own location if it was a different color. It doesn't stand out as much when it's the same color as other things on the map, just with an asterisk on it.
After picking your location on the map it should probably give you a link to go back to the main GsG page instead of to the forums.
When creating a new event if the user has no social groups the dropdown should be filled with something like, "(you are not a member of any groups)" instead of just being empty. Empty dropdowns look bad.
When searching on the main page it was not immediately apparent to me that it had worked. The search area dropdown reverted to 100 and I didn't see anything new on the map. It took me a while to realize that the search results were below the map. You might want to either put the results above the map or include a little bit of text above the map that says something like "Found X members, Y groups, and Z events. Jump to results" with a clickable link to jump down to the results.
If you click on a user's profile, then hit the back button, it should have your map zoomed into the same spot. Right now it seems to reset back to your "home" location.
Bugs/problems:
I think someone else mentioned this already, but when I go to add a new event I see this at the top of the screen:
Warning: Invalid argument supplied for foreach() in [path]/calendar.php(1828) : eval()'d code on line 61
Warning: Invalid argument supplied for foreach() in [path]/calendar.php(1828) : eval()'d code on line 70
When you click on a user or event on the map the name shows up in yellow text on white. Extremely hard to read unless you mouse-over it.
Question:
My brain often has a problem wrapping itself around time zone changes and DST changes, so I don't know if this is just me, but I find "Maintain same time throughout the year, regardless of DST changes" a little hard to understand. Does that mean that if I pick 5 PM Eastern and check that box that the game will always be 5 PM Eastern, regardless of whether we're in DST or not? And if the box was unchecked then when DST changes it'll be shifted an hour (to 4 PM or 6 PM, depending on which change happened)? It might be nice to include a little example in there for people like me who are time-zone challenged.
Is there a way to type in an address to set your location, instead of picking it from the map? If not, this would be nice to have. At the very least it would be nice to type in a location and get the map to center there, then you can zoom in and click the screen to set the location.