"--ignore-case" is only available for the 'diff' cvs command.
So, I guess it's either hack-the-source time, or just spend the time to normalize the case in your files.
I was thinking you may be able to use the 'commitinfo' file to create a case-insensitive regex that will trap the commit and enact it on the *real* file, but the more I think about it, the more I think it would just cause an endless loop. Plus, it would only work for commits, not for checkouts.
I think the path of least resistance is just to normalize the files...