You know your players are whiners when...
* You have done your best to answer their complaints/criticisms and they *STILL* whine about the game.
* You aren't having fun.
* You find yourself saying "Because I'm the DM!!". (Note: This may also indicate that you should start taking a nice hard look in a mirror...)
* The magic items listed in the DMG, SRD, or rules-abusing 3rd party supplement "aren't powerful enough."
* The players say, "We aren't powerful enough," after they've wiped the floor with those CR 20-24 demon prince avatars (yes, plural) from FC1... at 10th level.
* You go to your next game with a degree in D20 Game Rules just so you can start the adventure.
* They deliberately try to take on an advanced ancient great red wyrm after you've warned them repeatedly about how outmatched they are - in those exact words - and get a TPK, and then complain that you're a killer DM... when their characters are 3rd level.
I could go on.
Please note that many of the above indicators also apply to a DM who's not listening to his players, and is about to find him/herself alone at the gaming table.
