When multiple people are working with CVS, what can sometimes happen when you do a “cvs update” is that binary files get “merged” as if they were text files. Naturally, this can cause some file types to become corrupt.

To avoid this happening, type:

$ cvs admin -kb path/to/binary.file

Usually, you have a large number of these files (in my case, I had about ~1000 zip files). So combining the above with Bash’s find can be very useful. Assuming you are in the working directory:

$ find . -name "*.ext" -exec cvs admin -kb {} ;

The “{}” substitutes the found file, which CVS marks as binary for you.

There is also a handy guide on working with binary files in CVS.