Ok, this reply is aimed at all the people who suggested that this rule for scrolls is NOT an obscure one, or that I should have known about it because it directly related to my PC.
1) First, like I said, at our table the DMG is not exactly used by the players.
2) Please tell me how a CLERIC is supposed to be familiar with the "Use Magical Device" rules when this is an EXCLUSIVE ability that only Bards and Rogues have?? I did NOT know I needed to be familiar with the abilites of those classes before I choose mine. Gets back to having to know ALL the rules first before creating a PC, doesn't it?
3) Nowhere that I can find in the PHB does it tell you EXACTLY the 10+INT rule applies to scrolls as well. Sure, it makes a mention in the "use magical device" section that you need a high INT, but without that specific INT formula in black and white, that can mean anything. Heck, my "lowly" intelligence of 12 IS considered high or at least above average right? The vague reference to the DMG does not help me since, like I said, I couldn't use that book as a reference. So bottom line, the PHB, the book meant for PLAYERS, does NOT state the 10+INT rule for scrolls anywhere. If I am missing it, please let me know the page number, because otherwise what you guys are telling me is that in order to understand my Cleric-given ability I needed to know something about a rogue's ability which then makes a vague reference to ANOTHER book that I am not even allowed to look at. Yikes! So, yes, this IS an obscure rules for scrolls, dammit!

Even Wippit Guud left a message to the affect that he didn't know about it after playing Wizards for a while. And I am playing a cleric! Can you blame me for being clueless?
4) INT is not the only stat you can use to read arcane scrolls. Sorcerers are allowed to use their CHA. Sure, the PHB mentions that my PC is supposed to use the domain ability as a Wizard, but I have seen lots of cases where spells are passed between classes, due to some special ability or other, and it changes their requirements in some way, like material components are dropped or something. Why not this as well? Why can't a cleric of Mystra conceivably use his WIS for this Goddess-given ability? Again, it was never mentioned clearly. But, this point is actually moot, because like I mentioned way back when, I was not aware of ANY kind of high ability score was needed for scrolls, WIS or otherwise.
5) I am actually lucky. Can you imagine if my INT was a 10? That is a perfectly common score, one I could have very easily wound up with on INT, yet it would have meant NO scroll-casting for me. You would have seen some SERIOUS ranting then!

I feel bad for all those uninformed clerics of Mystra out there with INTs less than 11.