This issue is caused by CVSNT (the CVS client used by
TortoiseCVS), not by TortoiseCVS itself.

Please note that all communication with the CVS server and
all modifications of files in the sandbox is done by CVSNT, not
by TortoiseCVS.

Therefore, this issue cannot be fixed in TortoiseCVS; you need to
report the issue to the CVSNT maintainers using the mailing list
at http://www.cvsnt.org/cgi-bin/mailman/listinfo/cvsnt. When
doing this, be sure to include the version of CVSNT you are
using; you can see this in the About dialog of TortoiseCVS.