The Documentation on the SharePoint Flex Response plugin is not 100% correct.
When editing the Plugin.properites file and adding the following line...
com.symantec.dlpx.flexresponse.Plugin.plugins = SharepointQuarantine.jar, SharepointReleaseFromQuarantine.jar
MAKE SURE THE THAT THE SPELLING is PERFECT - This ALSO means the capital P in Sharepoint.jar.
If the CASE of the letters of the file and what is in the properties file is not perfect it will NOT load.
The files that you copy ot the plugins directory are:
SharepointQuarantine.jar and SharepointReleaseFromQuarantine.jar so make sure the properties file mathces the case letters of the actual file.
Nice catch. thanks for posting.