I have 6 Jenkins jobs that use the CVS plugin. When I updated the CVS plugin from v2.8 to v2.9, all of these 6 jobs disappeared from my Jenkins dashboard.
When I downgraded to v2.8, the jobs reappeared.

Here is the relevant part of a typical configuration file:

<scm class="hudson.scm.CVSSCM" plugin="cvs@2.8">
<flatten>false</flatten>
<repositoryBrowser class="hudson.scm.browsers.ViewCVS">
<url>http://lagoon.hq.sag/cgi-bin/viewvc/viewvc.cgi/</url>
</repositoryBrowser>
<repositories>
<hudson.scm.CvsRepository>
<cvsRoot>:pserver:anonymous@lagoon.hq.sag:2401/FS/fs3073/Repositories/DocSources</cvsRoot>
<repositoryItems>
<hudson.scm.CvsRepositoryItem>
<modules>
<hudson.scm.CvsModule>
<localName></localName>
<remoteName>Owwep-cep-clientapi</remoteName>
</hudson.scm.CvsModule>
</modules>
<location class="hudson.scm.CvsRepositoryLocation$HeadRepositoryLocation">
<locationType>HEAD</locationType>
<useHeadIfNotFound>false</useHeadIfNotFound>
</location>
</hudson.scm.CvsRepositoryItem>
</repositoryItems>
<compressionLevel>-1</compressionLevel>
<excludedRegions>
<hudson.scm.ExcludedRegion>
<pattern></pattern>
</hudson.scm.ExcludedRegion>
</excludedRegions>
<passwordRequired>false</passwordRequired>
</hudson.scm.CvsRepository>
</repositories>
<canUseUpdate>false</canUseUpdate>
<skipChangeLog>false</skipChangeLog>
<pruneEmptyDirectories>true</pruneEmptyDirectories>
<disableCvsQuiet>true</disableCvsQuiet>
<cleanOnFailedUpdate>false</cleanOnFailedUpdate>
<forceCleanCopy>false</forceCleanCopy>
</scm>