A few clients have reported this identical problem. It is not a DBC-specific problem. It is caused by a Hewlett-Packard printer driver application.
In a DBC program, when printing to an HP-brand printer it may use the generic all-in-one software driver called the HP Universal Printer Driver. In this is so, there is a process called hpmup###.bin or hpmup094.bin which locks the DBC Finance datafile.
The HP Universal Printer Driver's behavior is incompatible with DBC Finance's requirement that it have exclusive, uninterrupted access to its own datafile. DBC Finance cannot read or write to its datafile if it is locked by the HP Universal Printer Driver.
There are a number of posts on HP's support forums about the HP Universal Printer Driver locking the files of other programs besides DBC programs.
To unlock the DBC datafile, you have to terminate the hpmup###.bin process using the Task Manager. Terminating the process unlocks the file, and allows DBC Finance to open it again. If you log off or reboot your computer, the hpmup###.bin process is terminated automatically.
For a permanent solution, the HP universal printer driver has to be replaced with the native, non-generic driver software for the HP printer you use.