My application running on a Windows server makes use of a Jet/Access database. For some reasons around every two weeks that database file gets locked by the System process (
Here's another possible cause I've found:
There is a bug in Windows 7 and likely in Windows Server 2008 (possibly 64bit versions only). It surfaces when you disable Application Experience service and causes the same problems as described in the question.
Re-enabling this service has fixed this problem for me.
A bit more info here as to why it's causing a problem.
List of other SO questions which seem to be related: