vc failure: Wrong type argument: stringp,nil

[thekhirgan]

Howdy.
I'm trying to use vc in xemacs v21.4.  I have an issue when trying to
check out specific versions of a file, i.e. issuing a

C-u C-x C-q 
Branch or version to move to: 1.2

sequence.  RCS successfully checks out the file and replaces the
working file in the active directory, but xemacs then fails with a

Wrong type argument: stringp,nil

message.  I've poked around manuals and newsgroups for a solution, but
haven't turned up anything I can use.  I admit I'm lisp-illiterate.

Thanks in advance,
TheK