As presented in the user group: https://groups.google.com/forum/?fromgroups#!topic/jenkinsci-users/Dvv0I3FBNW4

We've been running Jenkins 1.451 and 1.454 on Windows XP against a CVS repository for a few weeks now, without any problems. The CVS plugin (v1.6) was using the local cvsnt install.

We've since upgraded the CVS plugin to version 2.1 (by manually pinning the plugin) and since then, CVS changes are not detected. The CVS polling log is triggered properly, tons of "cvs rlog" instructions are sent, but at the end "No changes" is displayed.

Using CVS plugin 1.6 the cvs polling command looked like this (executed at 5:26:21 PM EDT):
cvs -q -z3 -n update -PdC -r d-chg00014229_op_brc_preimp-op-2012-02-27 -D "Thursday, March 22, 2012 9:26:21 PM UTC"

Using CVS plugin 2.1, the last cvs checkout command looked like this (executed at 11:56:16 AM EDT):
cvs checkout -P -r d-chg00014229_op_brc_preimp-op-2012-02-27 -D 23 Mar 2012 11:56:16 EDT -d portailInt portailInt

We're in Montreal, so Eastern Time Zone with Daylight Saving Time in effect.