Autostart 5.2.2 'Path Failed' Error Starting Backbone Service

Hi - I am running a 2 node Autostart 5.2.2 SQL cluster, and I am having a problem with one of the nodes - I am unable to start the backbone service.  This cluster was working fine for a couple of years, and I just notice a few weeks ago that one of the nodes wasn't running.  After a little digging, I found the following in the backbone log file:

ID00004722 Backbone release V3.3.1 #106 Dec 7 2006 02:00:00

site is now coming up, site-id <1> log_dir <..\log\backbone>

detect site-failure after: 120 secs

failure detection parameters: ratio=1/2 min=50

Backbone info Tue Nov 02 15:44:49 2010
ID00004353 restart Backbone: test

Backbone info Tue Nov 02 15:44:49 2010
ID00004530 Initial path to site 2 using ip=128.127.84.48 pxi=0x326398 ints=1

Backbone info Tue Nov 02 15:45:06 2010
ID00004549 Recompute site 2/125's IP address to 128.127.84.48: Path Failed

Backbone info Tue Nov 02 15:45:14 2010
(This repeats about 10 more times, but I thought I'd keep this a little shorter)

ID00004549 Recompute site 2/125's IP address to 128.127.84.48: Path Failed

Backbone info Tue Nov 02 15:46:45 2010
ID00004365 : shutdown (termination of detected)

I don't see any issues on the server with the network connection - I can ping back and forth between the servers on either NIC - any ideas?

Thanks,

John