Flummoxed by Connection Problem

[DesCF]

Everything was working fine until suddenly this problem appeared from
nowhere:

Boot up the pc and go into SQL Server Management Studio. The database is
present and the data can be accessed.
Go into VB2005 Express and run the project. Everything works fine.
Open Database Explorer and connect to the database and the following
happens:
1. The project no longer works and this error appears at cnn.open()
'Cannot open user default database. Login failed. Login failed for user'
2. The database is no longer available in Management Studio. It appears
but no longer has the little + sign next to it and the data is no longer
accessible. If I try and view the database properties I get this error:

Cannot show requested dialog.
ADDITIONAL INFORMATION:
Cannot show requested dialog. (Microsoft.SqlServer.Express.SqlMgmt)
An exception occurred while executing a Transact-SQL statement or batch.
(Microsoft.SqlServer.Express.ConnectionInfo)
Database 'T:\VS_DATA\NORTHWND.MDF' cannot be opened due to inaccessible
files or insufficient memory or disk space. See the SQL Server errorlog
for details. (Microsoft SQL Server, Error: 945)


The only way I can get out of this situation is to reboot my pc. I am ok
as long as I don't try and connect to the database via Database Explorer.
I have tried disconnecting from and even deleting the database in Database
Explorer to no avail. HELP!




Des

 

[DesCF]

I have narrowed down the sequence:

If I close the connection to the database in VB2005 Database Explorer
(very important) and then restart the server my project works again. But
as sonn as I connect vian Database Explorer it breaks again.