Remounting a drive as read/write crashes the system and no dmesg.boot

[Scott Schappell]

Looking at info.0 I see:


Dump header from device /dev/ad0s1b
   Architecture: i386
   Architecture Version: 2
   Dump Length: 155131904B (147 MB)
   Blocksize: 512
   Dumptime: Fri Aug 21 08:27:45 2009
   Hostname: arthur.silvertree.org
   Magic: FreeBSD Kernel Dump
   Version String: FreeBSD 7.2-RELEASE-p3 #1: Fri Aug 14 13:27:47 PDT  
2009
     root at arthur.silvertree.org:/usr/obj/usr/src/sys/ARTHUR
   Panic String: ffs_sync: rofs mod
   Dump Parity: 2778312054
   Bounds: 0
   Dump Status: good

This is interesting:

"Panic String: ffs_sync: rofs mod"

It looks I'm guessing this is saying "read only file system  
modified".  So it looks like the problem is with mount?

If there's anything you want me to pull from the vmcore.0 let me know.

Again, this happens with the drive mounted RO from fstab. Unmounted  
then mount -o rw /backup.

Something is amiss, and first blush doesn't seem to be hardware related.

Scott