problem with 2.4.0test8 and 2.4.0test11

A few days ago, and again half an hour ago, X stopped working.
Both times this happened in a period of heavy and continuous
IDE disk access (copying a 12 GB tree from one disk to another,
and doing a diff between two 5 GB trees on different disks).

No mouse movement, no reaction to Ctrl-Alt-Backspace.
After killing the cp/diff process, X used 100% CPU,
and chvt would hang. After killing X and starting a
new one all was well. (Of course the vt will be garbled
again when I leave X.)

The kernels involved were 2.4.0test11preX and 2.4.0test8.
(2.4.0test11 dies here when masquerading, but 2.4.0test10
and earlier are OK.)

Andries