Error: "The file you specified cannot be opened. Make sure that it is not currently being used by another program or a read-only file. The Windows error is: The file exists"
http://support.quickbooks.intuit.com/support/pages/knowledgebasearticle/1008354
Observed this with both QuickBooks Premier 2007 and QuickBooks Premier 2008 when used on Vista Business in workgroup environment.
-BK
NOTE: As of 9/14/2009, Intuit has removed the original KB article from their database. The link has been updated. Please let me know if this is not helpful.