I have a few 7942G running on my network one of them is giving me grief lately, I will try and explain as much as possible as to what the problem is,
1. I reset the phone either through CUCM or simply taking out the cable and plugging it back again.
2. Phone boots and works fine for about 2-3 minutes.
3. The phone just stops responding, phone buttons response becomes ridiculously slow or perhaps delayed, receiving calls is impossible no response to off-hook position.
4. But works fine when I reset, then again for only 2-3 minutes
I have deleted the phone and re-added it again to no vain, the configuration is absolutely the same as the others which are working fine. The only difference I see is that the Individual Phone Button Template (the phone's own template) for the phone is missing.
Please any help would be great, thanking you all in advance.
A Phone Button Template is a required setting; you can't not have one.
Either you have a QoS/Firewall/Network problem that is interfering with that phone's ability to interact with CUCM; or, it's a defective phone. You can plug another phone in to the same switch port, give it the same IP address and see if the problem follows to the new phone. If it doesn't RMA the phone (assuming it's under warranty or SMARTnet). If it follows then you have to figure out what is interfering. Remember the phone is a dumb terminal; every button you press is sent to CUCM which tells the phone what to do. If CUCM never gets the SCCP packet or the phone never gets the response it'll be useless.
In addition to what Jonathan said. I have seen this problem with new phones (89XX) and they have been fixed with a firmware upgrade. Try installing the latest firmware version on your CUCM.