customized toolbars can come from a couple of different spots:
1. Built on the fly by a macro
2. Built by Tools|Customize
3. Built by tools|customize and then attaching them to a specific workbook.
My bet is you're writing about the second method.
These toolbar customizations are stored in a file called *.xlb (the name and
location vary depending on the version of excel and the version of windows).
I'd close excel and use Windows Start button|find (or Search) to look for
*.xlb. If you find more than one, note the locations and rename them all to
*.xlbOLD.
then back to excel to create a dummy toolbar. Then close excel and search for
the one you just created. (The location of the toolbars can vary based on your
upgrade path for excel.)
Now move each one of those *.xlbOLD files into that "real" folder that excel
used. Delete the dummy toolbar file and rename the *.xlbOLD to name that your
version of excel used (with the extension of .xlb.)
See if you can find the version the user customized.
If you find it (and it's the one they still want), keep that one and delete all
the others (just to avoid confusion later).
If none of them were the correct one, have the user create a new one (with just
a few icons). Then close excel and reopen. Did it save it correctly and
reopen?
If yes, keep building and when done, make a backup copy of this *.xlb file.
If no, then maybe something else is going on--incorrect permissions to write to
the folder that is supposed to hold the file may be the culprit. I'd get IT
more involved if that happens.
