Please ensure the following services are running and set to automatic on the PC Host:

PC Host Services
1. DataCollectionAgent
2. RemoteManagement Agent Service
3. Performance Center Agent Service
4. Performance Center Load Testing Service
5. Secondary Logon

If any one of these services above are not running, start it and configure the service to run properly.

Additional steps to check and confirm:
On the machine that is having an error connecting in Lab Management, on that machine open IE ''as an administrator''. Navigate to your ALM URL (http://[ALM SERVER}:8080/qcbin, and open Lab Management. If you can access this site, ensure the following:
* ALM URL is added to the ''Trusted Sites'' in IE's internet options
? In Internet Explorer, select Tools > Internet Options. The Internet Options dialog box opens
? In the Security tab, select Trusted Sites, and click Sites
? If you are not using SSL, ensure that the Require Server verification (https:) for all sites in this zone option is not selected
? In the Add this website to the zone box, enter the Performance Center Server internal URL (http://[ALM server name]:8080/qcbin), and click Add

* To confirm that the correct ports have been opened so the PC Host can connect and communicate with your ALM-PC environment, perform the following ''telnet'' command from a CMD: telnet [IP address] [port]
? Telnet form PC Host to PC server (ports 80, 54245)
? Telnet from PC server to PC Host (ports 80, 54245)
? Telnet from PC Host to ALM (port 8080)
? Telnet from ALM to PC Host (port 8080)

* Ensure ALL ports are open bi-directional

* Ensure that the { PC server - PC Host (Used as a Controller or Data Processor) } is in the same Domain as the ALM server and the ALM Database

* The clocks on the ALM Platform, Performance Center server, and database server are synchronized

* Check that all Performance Center Servers have the same version

* If the Communication Security passphrase on the Performance Center server/host and the ALM server do not match. The two products cannot communicate.

* Windows Firewall is disabled on all servers (ALM, ALM Database, PC server, PC Host, and SALG)

I hope this helps.