If the /home partition fills up, gimp will choke trying to
write to the swap file in ~/.gimp. No surprise there, but it
appears to get stuck in a loop reporting the error. Hundreds
of dialog boxes pop up reporting the write error. X is
unresponsive at this point. There's no way to stop it except
switching to a console & killing the gimp process.
Sadly, when I did this the X server did not recover. The
gimp windows all closed, but the server was so tweaked it
could not be shut down. The console hot-keys no longer
worked, nor did ctrl-alt-backspace. It took a ctrl-alt-del
to get the machine out of this state.
This seems to indicate a problem in the X server as well (S3
ViRGE, SVGA server).
The fix would require significant changes to the GIMP tile manager. I don't
expect for this problem to be addressed until version 1.2 of The GIMP. The GIMP
developers were aware of a problem in 1.0.x series.
Hopefully 1.2 will work better - it has significant tile manager improvements.