I tracked it down to the fact that fsck is dynamically linked. I rebuilt the
whole package and this is the default. If I build a statically-linked fsck,
everything works.
I have never seen this problem with any 2.0 or 2.1 kernel except this one.
The problem is easily reproducible.
I have e2fsprogs-1.07, ld.so-1.8.10, and libc-5.4.23 but I think the problem's
in the kernel.
Thanks