Newbie question: cannot open CVS/Root: No such file or directory error

[Schlitz]

I am receiving the following when I attempt to tag a file.  The same error
occurs when doing other things from time to time.  What would cause this?

cvs [tag aborted]: cannot open CVS/Root: No such file or directory

The error seems to mainly take place on the action after I do a cvs commit.
I can't figure out exactly why and when it happens though,  and I would like
to prevent it.  When does this Root file go away, and what am I supposed to
do to ensure that ?

Thanks
George