Hi James,
You may be running into a PoE problem here, depending on what type of switch/switchport is being used. If you are using an older model that only supplies Cisco Pre-Standard PoE it won't fire up the 7975G :(
The 7941G can use either Cisco Pre-Standard PoE or the new standard IEEE 802.3af PoE.
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=).
From this good doc;
http://www.cisco.com/en/US/products/hw/phones/ps379/products_data_sheet0900aecd802ff012.html
The 7975G can only use IEEE 802.3af PoE
Power Requirements:
Supports IEEE 802.3af PoE (Class 3). 48VDC is required; it can be supplied locally at the desktop using an optional AC-to-DC power supply (part number CP-PWR-CUBE-3=) or power injector (CP-PWR-INJ=). Local power options require a corresponding AC country cord
http://www.cisco.com/en/US/products/hw/phones/ps379/products_data_sheet0900aecd8069bdb7.html
Hope this helps!
Rob
