Excel 2003 on Win XP

A grid has been created to allow users to find the info they need (titles
typed into Excel cells) then jump to the appropriate resource (web page,
file, etc) by clicking on a link in the next column/cell. There are two
links causing problems, and they are both .pps files. The links are pasted
behind existing text, e.g. "Click Here", where the actual URL is added to
the URL location property in the URL dialogue box.

The link that is pasted in as the "correct" link references a .pps file on
an internal server, so the link that actually works is:

file://FSVR03LL/2201/SFS_Files/Training/Chl%20Water%20Cycle%20&%20Assay.pps

Paste it, then click on it in the excel sheet and it opens the correct file.
Save and close Excel, then re-open the Excel file that contains the links,
and the link no longer works. Opening the hyperlink shows that the path has
been changed to:

.../../../../../../2201/SFS_Files/Training/Chl%20Water%20Cycle%20&%20Assay.pps

Any idea why this might occur, and if it is an Excel thing, how to make it
retain the original, working link? The user showed me this phenomina all at
once, so there was no disconnect from the network for Excel to think the
link wasn't valid.

Thanks,
Keith