Hi Terry,
I would try deleting all the gz files from the \web\scripts and \web\styles folders.
Then run GzipAll again, and try again.
If that fails I would test the program with "combined" and "precompressed" turned off. If this also fails then the error is in the CSS file itself - either the CSS or how the file is plugged into the app. If it succeeds then we look closer at gzip.
cheers
Bruce