I tried the PRAM reset while the HDMI cable was connected--it didn't work with my rMBP and the projector to which the HDMI is attached.
My Apple rep isn't back at work until Tuesday, so I don't expect to hear anything more until then. Of course, maybe there will be a surprise update of 10.8.3 and/or a new rMBP firmware before then.
I know that with some external monitors or projectors there is no problem, but I don't know what the variable is here. The answer may lie in that variable. Also the fact that a Thunderbolt-DVI connection works, but not, apparently, a TB-HDMI connection.
And it's still not clear to me whether this problem exists /only/ with the rMBP, or also in other MBPs using 10.8.2. And if the problem exists only with the rMBP, how do we know whether it is the 10.8.2 update or the firmware update that came along with it? The firmware update sort of installed itself silently along with the 10.8.2 update in most cases.
At the end of the day, this is a bug that Apple will have to figure out and fix. What makes no sense is that the OS update and/or firmware update were issued without sufficient testing of the rMBPs and an HDMI connection, and that they still haven't come out with a fix. Maybe they're too busy working on the iOS 6 maps.