I'm running X Server 1.6.2 with Intel DDX 2.8.0 and Linux 2.6.29.
Everytime there's a write/update on GNOME Terminal, all of Compiz briefly freezes. This even happens when the window's minimized. Opening a new tab in the terminal and switching away from the busy one aleviates things.
Ouch... I've seen that before but in 2.6.x drivers.
Make sure you've got all of UXA/DRI2 enabled correctly in the X log - sometimes things look like they're working fine but it's actually not hw-accelerated.
If all else fails, try using a non-antialiased font instead, or change the setting compiz uses for generating thumbnails (it should have an option to ignore minimized windows).