Not sure if this issue got resolved for you but I wanted to pass on this fix that Microsoft issued for this particular error :

Cumulative Update 4 for SQL Server 2005 Service Pack 2 (build 3200)

http://support.microsoft.com/kb/937343

Apparently this error then causes the sql server to shutdown inadvertantly, and if you are running in a cluster then it may failover or may have to manually failover and re-start SQL.