Thank you for the suggestions. I've redone the update of the Base multiple times, including redownloading the update and remaking the black module, and I keep getting the same 6-blink error code.
A few additional notes that may help to hone in on the problem:
Every time I run the Base update--that is, AFTER the first time I tried to update the Base (see below*)--the CAB-2 reports that the Base is running v. 1.6.
I seem to be able to access the changes from 1.54 to 1.6 on the CAB-2. Would I be able to do this if the Base were not also updated?
Can someone who has 1.6 tell me if when you power up the CAB-2, the screen that appears is not the CTC screen, but the last screen you were using before powering down?
*The very first time I tried to update the Base to 1.6, the CAB-2 was in the Base, which was on a shelf under my layout, and, because it was dark (!), I inadvertently put the Base module into the port in the CAB-2, which was an inch above the port in the Base. Of course, the update didn't run that time. Is it possible that that first unsuccessful attempt to update the Base without the module in the Base port activated the 6-blink error code and that, since then, the updates have been successful, but that, for some reason, the error code will not go off?
Keith