Problem with message box on IE7/8

[Atoa]

I having an really annoyng problem with the message boxes on the IE7/8.

If the message is too large, the roll bar don't stop in the right place when writting messages.

Eg.: I want to select the last line of the message with the mouse to add an BBC. if i try to do it, it's selects almos all text and return no top.

This can be partially solved by using the "Compatibility" function, this solves the message box issue, but break a lot of parts of my theme.