Trouble opening pst-file

I’m in the middle of installing a nas-box (IBM 300G nas-gateway) based on Windows2000. The rest of the environment is NT4-based. Everything works fine except outlook (97). We don’t have an exchange server, but use an administrative install. So everyone has his own PST-file. When we put the PST-file on the NAS outlook sometimes looses its connection tot the pst-file and you’re not able to send or receive mail untill you restart outlook. However this isn’t NAS-related, but Windows2000 (or XP??) related. If we put the pst-file on another (non-nas) W2K-server the same thing happens. If we put the file on any NT4 server everything works fine.

Any clues???
Can we expect this with other applications as well??