What did you send it in for? If something was replaced in it that required a driver, and the replacement has possibly a different driver, then your system may be waiting for a timeout response from the older driver.
I hope I didn't sound confusing, but basically, I would state that your system is trying to execute a command and the wait that you are seeing is due to the system timing out and then giving up.
One thing I had this problem with was my wireless. I don't remember which system it was, but the wireless drivers to execute my connection was being done after Windows was trying to restore my network drives. So basically - the system tried to access the drives, timed out and then loaded then executed the wireless routine. This created a hellacious wait that only happened with wireless - the LAN went faster (thus how I determined the problem). A quick reload fixed that problem.
Try to backtrack what was done and maybe you can identify the issue.
Hope this helps!