Bug#642703: general: Scan lines appear in drop-down menus. LibreOffice also shows artifacts when starting. Might be something to do with the version of fglrx.
Do you have swap space enabled?
How much memory do you have?
I get this problem, including font corruption (one or two characters per
font), whenever I run something that causes the system to start using
For me, it seems to happen most to Gnome apps, including Google Chrome.
Did you notice excessive hard disk activity when you started the
program, I mean, apart from the activity involved in loading the program.
Check: try closing other programs first, starting LibreOffice, and see
if there's any difference.