MS-Access Mult-user - Vista set of PC-s on a network

I recently migrated to a new set of PC-s for a small shop, 5 PC-s, from a set
of XP-Pro OS system to a set of Vista OS computers. We are now having the
problem of only one person in the database at a time.
If you are on the network PC you can always get into it. Only one of the
other PC-s can get into the database. The 2nd PC that attempts, clocks
forever. I have checked everyone on the premissions, I have checked every
PC that within MS-Access it marked share, I have turned off the Norton
firewalls, I have created a c:\temp folder on all the PC-s. Still the
problem exists any ideas anyone?
Thank you Russ