Panic: vrele: negative ref cnt

[Robert H. Perry]

I received a panic message (see Subject) yesterday following a GNOME
upgrade.  The upgrade was successful but I encountered subsequent problems
trying to access Firefox websites and my mail site in Thunderbird.  I
noticed a Plugin error message in Firefox and prepared to paste it into a
message to the mailing list but was unable to get a connection and
eventually lost it.

I reset my modem several times then decided to reboot.  First, I re-enabled
my firewall then entered shutdown -r now.  Next I received the panic message
and a repeat of the following:

READ_DMA ad0:Timeout - Read_DMA retrying (2 retries left) LBA = 28162271
READ_DMA ad0: FAILURE -READ_DMA status=51 <READY, DSC, ERROR> error = 40
<Uncorrectable>  LBA =28162271

Unfortunately, this may not have been exactly how the message read.  I was
sort of in a panic state myself.
Another message indicated there was no request/requirement to dump.

I run FreeBSD 5.4 RELEASE.

Your advice is appreciated.  Thnx,
Bob Perry