Well, this did not end well. As you can see from Nigel's SNMP data for my site, right after I installed firmware v6.12 at 9pm, my wireless signal strength dropped by about 10dB. In other respects, everything seems to work, and I at first I thought perhaps it was the rain. However, we've had rain on and off all day, and as you can see from Nigel's site, the signal strength was fairly uniform until the very sudden drop at 9pm. Reboots did not solve the problem, so I reverted to v6.10 using the "downgrade" command line option. That did not improve the signal strength, so I upgraded back to v6.12. I checked all the configuration settings, and everything looked normal. Data transfer through the radio worked fine. So, I decided to reset the configuration (using the command line) to make sure nothing had changed. I'd done that a couple times a month ago, with no ill effects. However, this time it appears to have "bricked" the radio. It draws about 160ma (about the value from a week ago, when I first measured it). There is no light on the side of the unit, and the Ethernet port is dead. I'm going to bed. Sunday morning I will go out onto the roof and attempt to reset the unit via the pinhole. I hope this is not indicative of MikroTik quality. I'm glad the thing is not up on a tower ...