Just recieved a 7941G phone. Currently have a 7940 on my desk, PoE. When I try to plug in the 7941 to the network (using the same cable as the 7940), nothing... no power, nothing. I have a spare power cube, so I plugged the 7941 in using that, and the "Ethernet Disconnected" message displays. Plug my 7940 back in and it powers up and registers fine.
This really sounds like a cable issue. When you plugged the Power Cube in and received the "Ethernet Disconnected" message on the display, you have proven part of the puzzle (that the existing cable that went from the wall jack to the 10/100SW on the base of the phone is not connecting for some reason):) Try isolating and replacing all the cables involved and probably even leave the PC cable out of the equation.
You should be fine for power as both the 7940 and 7941 are Class 2 devices. Have a look;
The 7940G/7941G and 7960G/7961G are class 2 devices (7.7 watts) and the 7941G-GE/7961G-GE phones are class 3 devices (15.4 watts).These are not configurable settings.
The 7940 uses only Cisco Pre-Standard PoE whereas the 7941G can use either Cisco Pre-Standard PoE or the new standard IEEE 802.3af PoE. The reason that I think the problem is perhaps with the cable is because of the report on the 7941 display that indicated "ETHERNET DISCONNECTED" used the external power supply. This is really just a suggested step here in trying to Troubleshoot the issue. It seems "odd" that this could be the case but I have seen stranger things happen. I have also plugged the cables into the wrong Jacks on the base of the phone and gone on to try and solve this problem only to realize what an idiot I am sometime later :)
Power Requirements The phone is interoperable with Cisco Pre-standard PoE and with IEEE 802.3af PoE (the phone is a Class 2 device); 48 VDC is required; it can be supplied locally at the desktop using an optional AC-to-DC power supply (part number CP-PWR-CUBE-3=).
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...