editing hyperlink (ctrl. K) causes error

I use Frontpage 2003 for a long time now, but recently every time I try to
edit an existing hyperlink with ctrl-K or the "Insert Hyperlink" menu, an
error pops up saying:
"C:\DIRECTORY is not accessible.
The process cannot access the file because it is being used by another
program."
I can click that off and edit the link, but the list of files in the
directory isn't displayed. And the error-popup is really annoying when I need
to change a dozen or more links in a document. I tried the
"repair"-installation but it didn't help.
I can't say exactly when this started, but I suspect after I installed the
McAfee virus-scan; the support had to fix a few things in my computer. I
hadn't any trouble before when I ran the NortonAV, but Symantec won't support
my Windows 2000 any more.
Anybody might have any idea what's causing this problem and how to fix it
(short of de-installing the AntiVirus)?
Thanks so much for help!
* * * * Aeshna