I have an what appears to be a five digit integer in cell "A1" which has a
very strange property. If I type the same five digits into cell "A2" and
then in a cell "A3" type the function =if(Range("A1") =
Range("A2"),"Yes","no") the result is "no". If I then double click cell
"A1" (as if I wanted to edit) and hit the enter key, the function value
magically changes to "yes". The strange integer was copied from the zip code
field of an address file.

Can anyone please tell me what's going on?