Copied MS Access db from Win 98 to Win NT

I developed an application that uses a MS Access database. On a Win 98
system it all works fine. If I install the application on Win NT and copy
the database file to the Win NT system as well, suddenly the application
can't open the database anymore. Error message tells me the database is
being used by another user!? I checked the database file and the path. It
all belongs to the same Win NT account from where the application is
being started. Any ideas?