I've moved your post to our ePO area. Hopefully a product expert can help you soon.
Do you have a solution for this? I have upgraded my ePO 4.0 to 4.5, now I have the same problem.
The first place to look for errors relating to pull and replication tasks is the epoapsrv.log on the epo server. Try doing a pull task, and when it fails, check the end of the log for errors (or post it here and we can have a look.)