CVS proxy itself can work on CVS NT. However latest version of CVS NT (wich
are shipped with plugin) may not.
However this is not a problem. Just open plugin configuration window
(start\Program\Pushok Software\CVSSCC\Configure plugin) at "CVS executables
page". Type the path to cvs.exe that is shipped with WinCVS 1.2. This way
plug-in will use the cvs.exe (cvs client) that is compatible with your
system and cvs server.
You can look also to this faq section:
http://www.pushok.com/soft_cvs_faq.php?#2