moving this to the correct area...
can you tell the agent to talk back the the epo server from the agent gui and then post the agent log for that period so we can see whats wrong.
or if you have no access to the local gui just post the entire agent log as a text file attachment
I am also unable to get Agent 4.5.1 to connect to ePO 4.5 and I have installed all of the most recent patches and extentions to ePO. I have tried from Windows 7 32-bit and 64-bit.