Under Windows 7 RC, if I run backup with the "Show details" box ticked, the usual information scrolls up the window until the backup gets about halfway through.
At that point it gets corrupted with some text repeated and/or control characters appearing in the window. Sometimes the machine starts to beep (CTRL-G presumably). The window then closes though the backup appears to complete normally.
This didn't happen with the previous beta of Windows 7 and it doesn't happen with XP.
I'm guessing it's some sort of buffer full/overflow issue and there may be nothing you can do about it, but I just thought I'd mention it.