The "All sessions are busy -check for extraneous consle logins" means that all responding agents have an existing session so can't allow the user to connect. However, the agents stuck in the customising state are those that have not successfully started and reported their status to the connection server - please check that you're not hitting http://kb.vmware.com/kb/1005991 and that the support tool (c:\program files\vmware\vmware vdm\agent\dct\support.bat) runs successfully on your VMs.