Are all the devices involved on the same VLAN? Has this setup ever been able to monitor an agent? Does monitoring work if you use Cisco Agent Desktop?
What system are you referring to? Describe your installation in some detail - version numbers etc. The more you provide, the better the assistance.
Did you get this resolved? We are having this issue with remote users as well when using desktop Monitoring,we are currently spanning,which only allows in house agents to be monitered.Cisco has stated that it may be drivers need to be updated on the NIC card