[Samba] shared XL file problem

[phwashington]

We are currently having a problem with a shared XL file on a samba
server.  There have been no changes to this server in a couple of years
and this file has been in use during the whole time.  This problem all
of a sudden just cropped up about 3 weeks ago.

UserA cannot open the file ThisFile.xls.  All other users can.
If all users connections are dropped from the file and sharing is
stopped then UserA can open the file and allow sharing on the file and
then all users can open the file except for UserB and UserC.
So if we knock off all Users and discontinue sharing then UserB and C
can open the file and allow sharing, but then UserA cannot open the
file.  This is independent of whichever computer the User is on.
In the mean time there are 20 other Users that do not seem to be
affected by this.
When I say user cannot open the file: The user is given an error message
"Excel.exe has generated errors and will be closed by Windows. You will
need to restart the program"

I have looked at the permissions on the samba server and UserA, UserB
and UserC all seem to have the same permissions and are members of the
same group.

Samba 2.2.7



Any ideas?
What else can I look for?  
Has anybody seen anything like this?
I don't think this is really a samba issue, but since there are a lot of
people here that no about file sharing in Windows/Linux environments I
thought I'd ask?