I'd try opening excel in safe mode:
close excel
windows start button|Run
excel /safe
then File|Open
Safe mode will disable lots of stuff--macros and toolbars, for instance.
If it turns out you can open the workbook, maybe it's not the workbook with the
problem.
It might be your *.xlb file (where excel stores your customized toolbar
settings). Close excel and windows start button|Find/Search for *.xlb (search
for hidden files and through hidden folders, too.)
Rename all of the *.xlb to *.xlbOLD.
Then reopen excel and try your workbook. If it opens, delete those *.xlbOLD's
and rebuild your customizations.
If it didn't open, then rename the *.xlbOLD back to *.xlb.
You might be able to recover the file by using another program--OpenOffice has a
better reputation for opening files that excel couldn't. (and I've seen posts
that say that xl2k may open files that xl2002 couldn't!)
(
http://www.openoffice.org, a 60-65 meg download or a CD)
If the file is really important, there are commercial recovery services. I've
never used it, but you might want to check into:
http://www.officerecovery.com