MS Access and Excel 2000 over network problem ??

[Help]

I am running XP on a LAN, Office 2000 Professional.

Whenever I have an Access document open (from the server
at my workstation), if I open an Excel document, the
figures in the Access cells all turn to "#" symbols. The
Access file then is unreadable and must be closed.

Any idea what to do to stop/ remedy this?
What causes this?

I have to close everything down again and again to get
both running.

Thank you in advance!!

H