I have a brand new 7941G phone that we attempted to change from SCCP to SIP for testing. We placed the contents of the firmware zip file into a tftp directory and pointed DHCP option 66 to that tftp server and started the upgrade process. The phone grabbed the term41.default.loads file serveral times over several reboots but now it appears to be stuck in a loop. It no longer tries to pull any files from the tftp server, it just sits with the upgrading screen and then occasionally reboots itself. It is getting an IP address, so that we know is working.
That is the problem then. Does the phone display the Cisco Splash screen, but with a circle with a dot in it bottom left hand side, and after a short while come up Auth Fail? If so, that is the phone being unable to find a suitable firmware version.
If this is the case, download and put the 8.5.2 & 8.5.2SR1 firmwares on your TFTP server ( copying 8.5.2 last, so the correct term41.default.loads file is present.
The phone should then be able to upgrade to 8.5.2, then 8.5.2SR1 and finally to 8.5.3.
We've given up on 8.5.3 for the moment and set our default load to 8.5.2, as this is the last version that new phones can be upgraded from without manual intervention.
Hope this helps, and let me know how you get on.
First thing I always try when having firmware issues is removing the voice vlan then configuring the access vlan with the voice vlan number. This of course assumes your 7941 is connected using a voice vlan.
You might also attempt to load the SCCP firmware again and restart the process.