"adb logcat" shows that pretty much everything in /data is missing.
I can't get root to investigate much further. I installed update.zip from this thread:
which gave me su and busybox, but su just reports "Permission denied" and logcat shows
E/su ( 3315): stat failed with 20: Not a directory
W/su ( 3315): request rejected (2000->0 /system/bin/sh)
(in recovery mode, the stat fails with 2: No such file or directory instead). "su -s /system/xbin/busybox" fails in the same way.
I have /system/app/Superuser.apk, but given that nothing is really running due to the state of /data I don't think that helps. I can't see what's in /data due to not having root though.