Errors Detected In File Since SP3
 

We're running Office XP and recently started installing SP3. On one PC
since installing SP3 when the user opens certain Excel files they receive a
prompt that says errors were detected in the file. This doesn't happen with
all files, just some files. If the user goes through the repair process and
saves the file all is well and the error doesn't occur again for the same
file. This never happened before SP3 was installed.

Are there legitimately errors in some of the user's Excel files that were
previously undetected without SP3 or is something else going on that can be
fixed?