Can't open file already open

Have a small network with XP and Vista machines.
If an excel machine has say myFile.xls open and another XP machine tries to
open this file they receive the message "File already open, do you wish to
open as read only".
Whereas if the Vista machine tries to open this file it just hangs and will
not open unless the first machine closes the file. No advice that the file
is already open etc.

How do I diagnose this problem.
Thanks

This is happening to me also. I am running both 2003 and 2007, although
it also occurs on machines only using 2003.


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sr_sparky