No CVSROOT?

I keep getting the following server message when I try to commit a file that is down one level in a directory. Can anyone tell me what's causing it and how to fix it?

Thanks

cvs release: No CVSROOT specified! Please use the `-d' option
cvs [release aborted]: or set the CVSROOT environment variable.

Please tell me the command that it was given (BEWARE: replace the password from the command with something else).