There are several possible solutions:
1. Use client which is compatible with your server.
You need to configure plug-in to use CVS client (CVS.exe) from either
WinCVS, Tortoise or better CVS NT distribution. This can be done on "CVS
Executables page" of plug-in configuration. You need to switch on checkbox
"Use specified" and point to CVS.exe location. For more details check this
page:
http://www.pushok.com/help/cvsscc/index.php?redirect=ui_config3.htm2. Use CVS in client-server mode
Currently you use CVS in client-fileshare mode. I.e. cvs.exe directly
modifies repository, being client and server in the same time. This is
enough dangerous because:
a. Accessing repository from very old client may just destroy it.
b. Known problem accessing repository as network share.
When you access your CVS NT repository via normal network protocol (:sspi:
:pserver: ...) you not directly access repository, it is accessed by server
software. So you'll have less potential problems.