In both MS Excel 2003 when the 3 character is entered alone in a cell it
changes to a 5 character when the cursor moves to another cell. This happens
in all excel files on the computer.

(Note that this also happens in MS Word 2003 when entering a "stand-alone" 3
in text)

In other situations (Notepad, Netscape mail) this does not occur.

We use McAfee VirusScan 10 which is completeley up to date. Full scans have
been carried out in normal and safe mode as it was assumed this problem is
some sort of macro virus. McAfee finds no problem.

We have tested different keyboards.

When a 3 is entered as part of a larger number there is no problem.

There are no apparent macros running.

Any suggestions as to what to try next?

Many thanks

David