Vista - Program on Vista OS accessed from Network's XP-OS computers but not from Vista comput

I am running into trouble running a program on all my computers on my network. I am using a book inventory software called Booktrakker. The program uses an Access database file system and theoretically runs perfect on networks.

My database has now almost 32'000 records and runs on a Vista Computer (replacing an XP-operated predecessor). All other satellite computers should optimally connect to this main PC but I noticed that only computers that have Vista on them have difficulty running Booktrakker. For some reason, not all Vista computers can connect simultaneously, and sometimes I do have to shut down Booktrakker on the main PC to have a satellite computer even start Booktrakker.

I played around with permissions on the main computer to basically give permission to "everyone" to access, read and modify the working Booktrakker folder without having any success.
Did I miss something in the networking/Vista? or it is just the program? Or it is just me?

Thanks

Have you checked with the folks that make the "Booktrakker" software about this problem? That would be the logical first step.

S-