X under valgrind?

[Nix]

I'm trying to track down a strange bug in X 1.9.0.901 (and probably .902
as well), whereby after a suspend/resume cycle long enough to time out
nonlocal TCP connections, my X server crashes the first time I map an
XEmacs window (probably 'the first thing that uses core fonts at all')
with this unhelpful backtrace:

Backtrace:
0: X (xorg_backtrace+0x28) [0x49b7d8]
1: X (0x400000+0x5dde9) [0x45dde9]
2: /lib/libpthread.so.0 (0x7f50fc27f000+0xe9b0) [0x7f50fc28d9b0]
3: /lib/libc.so.6 (0x7f50fb1f3000+0x731c0) [0x7f50fb2661c0]
4: /lib/libc.so.6 (cfree+0x6c) [0x7f50fb269abc]
5: /usr/lib/libXfont.so.1 (FontFileFreeEntry+0x8f) [0x7f50fbdf12ef]
6: /usr/lib/libXfont.so.1 (FontFileFreeTable+0x2e) [0x7f50fbdf136e]
7: /usr/lib/libXfont.so.1 (FontFileFreeDir+0xd) [0x7f50fbdf139d]
8: /usr/lib/libXfont.so.1 (FontFileFreeFPE+0x12) [0x7f50fbdf4692]
9: X (0x400000+0x2d04b) [0x42d04b]
10: X (0x400000+0x2fa8b) [0x42fa8b]
11: X (ProcessWorkQueue+0x21) [0x4307e1]
12: X (WaitForSomething+0x82) [0x456f72]
13: X (0x400000+0x2bf92) [0x42bf92]
14: X (0x400000+0x209ee) [0x4209ee]
15: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f50fb211d6d]
16: X (0x400000+0x205a9) [0x4205a9]
Segmentation fault at address 0xffffffff0241b148

gdb is not much more helpful (I mean, yes, obviously we have a
double-free(), but why? something to do with the font server I've got at
the end of the font path specifically to trip bitrot like this, I
suppose), so I'm planning to valgrind it... but I'm a bit chary of that
because the last time I valground the X server, horrible disasters
resulted which ended in a system lockup and massive filesystem
corruption. Of course, that was before the era of KMS: perhaps things
are better now that X hardly touches the hardware.

So... has anyone ever valground the X server? Does it work? (Of course
it will be slow. I'm expecting *that*.)