During initialisation Phone Manager does a number of tftp requests to the IP Office in order to get the internal users list, phone book, busy extensions etcetera.
The problem is that during one of the requests PhoneManager sends a "get" to the IPO tftp were it asks for specific info, ipo sends a message telling pm that the requested data is ready for download. PM does not start the download so ipo sends another message, if pm does not start downloading in a timely manner then you get that message in monitor.
It is related to either a very busy process on your pc or the network card is overloaded or you have a active virus scanner blocking the messages.
Create a new user account without any autorun applications and see if you get the same error then.