.xsession-errors filling with "Write error: Unknown error".

Every now and then my netbook runs out of disk space (it has an 8GB SSD). This turns out to be .xsession-errors filling with "Write error: Unknown error" over and over, as fast as it can log the error.

The culprit appears to be LMMS, as stopping LMMS stops the log spew.

This sort of error is, of course, typically something amiss at toolkit level. And, of course, LMMS is the only KDE/Qt app I regularly run (in Ubuntu 10.10 GNOME).

That said, this sort of error is also the sort of thing one finds in a casual Google, but I can't see anyone else having ever had this problem.

Any ideas?