Errors after startup

Only over the last couple of days has this been an issue. We do a daily reboot. After the reboot we get several events from MSSQLSERVER ending with an event in the event viewer:

17126 :
SQL Server is ready for client connections

Then almost exactly 50 minutes (50' 1") later we get:

17207 :
udopen: Operating system error 32(The process cannot access the file because it is being used by another process.) during the creation/opening of physical device C:\Program Files\MSSQL\Data\VTSystem.mdf.

and

17204 :
FCB::Open failed: Could not open device C:\Program Files\MSSQL\Data\VTSystem.mdf for virtual device number (VDN) 1.

This is one of our data files. From this point on we cannot connect to the database until we restart the service..

I have just recently been receiving the same error every night immediately following the backup job at 2AM. The application has 6 individual databases, 1 of which goes into a suspect state and returns this error. Each night it has been a different database, but the same aplpication. Any help is greatly appreciated|||

Check whether autoclose is set on the database, and if so turn it off. SQL Server opens data and log files exclusively at startup, and does not release those locks unless the database is closed such as by auto-close.

When data files are closed it's possible that a backup, virus scan or other process may come along and open the files,thus preventing sql server from re-opening the database.