XP Pro Intermittent Network Pausing

On a peer-to-peer network with about 9 computers running
MS Windows XP Professional SP1 w/critical updates &
patches, we are experiencing intermittent pausing about
once a week. The pausing began when we upgraded the OS on
the computers from MS Windows 98SE to XP Pro. On the
existing computers we performed an in-place upgrade of
the OS; new computers were added with XP Pro factory
installed. The pausing can last for up to 30 seconds and
each workstation shows an hourglass on the screen. On
days when the pausing occurs, it occurs frequently during
that day; however, several days can pass without any
occurance of pausing. One computer acts as the server and
stores all the data, every workstation runs Norton
Antivirus 2003. The main application used is a dental
database application, Dentrix. We have worked w/Dentrix
support to troubleshoot the application but they believe
it is a network issue (network adapters, switch, etc.).

How can we isolate or troubleshoot this problem?

Thanks for any assistance with this matter.

XP Pro Intermittent Network Pausing