Mike,
Thanks for your comments. I'll keep those in mind. I turned things off yesterday, and when I came back this morning, I reduced power to "low" and it worked okay. Then I brought the power back up in steps, and it keeps working. So I don't know what is wrong, but it's working now. When this first started, we were running a net with this station as net control. Took eight check-ins just fine, and then the rig stopped working. No one was at the transmit location, and nothing should have changed between the start of net and the failure. We'll just see what happens from here.
73,
W8WTD