I posted this question last night and Rick Rothstein gave me a possible
solution, but to no avail. Suspect Rick is not around at the moment becuse of
time zone differences, and I really need a solution urgently (because I can't
open heaps of folders):

I have a whole bunch of =HYPERLINK functions on one particular page. Every
now and then I have to recreate a certain group of them because of client
name list changes. All of the old ones such as:
=HYPERLINK("C:\0. QUO VADIS\","0. QUO VADIS")
still work properly, but now the new ones that are created e.g:
=HYPERLINK("C:\2. SETTLED CLIENTS\Dunn, P","Dunn, P")
come up with an error msg that the path "P" does not exist or is not a
directory. This has nothing to do with the comma in the folder name because
they have always been there. I can still open the folders by drilling down
from the top, so there's nothing wrong with them.

This came about because of the other problem that I'm having: when these
hypelinks do work (in a previous life) the folders open up subfolders in
separate windows, even though I have "same window" checked in folder options.
I noticed that if I used "Explore" instead of "open" then the same window was
used. So then I set a new default action of Explore
"C:\Windows\explorer.exe". I think I may have inadvertantly put the quote
marks in as well, but I can't remove the action now (or edit it). I notice in
the "Open" action that there is a checkbox for "Browse in same Window" but it
can't be checked. I think that would solve my separate windows problem, but
that is secondary to not being able to open them at all via = HYPERLINK


The only other thing that I changed was in the Worksheet_selectionchange
code, but because the new code didn't do what I wanted I commented it out.

I've restored the previous version of the workbook, but it does the same. I
have proved that it's not the hyperlink formula, but don't know what to try
next.

Thanks for any help offered. Brett