Ok, I'm not sure that I follow 100% about the new bug in the 990's S/W update.
I was going to be buying the 990/7125/LFM-1 combo.
My front L/R speakers are B&W DM603 Series 1, Center is CC6 Series 2, Surrounds are DS6 Series 1.
How would this sub bug effect my set-up?

It won't affect you unless you adjust your sub to -15db...and if you do that you have serious setup issues in the first place.

Stupid question but do you have a sub? I didn't see it listed. If you don't have a sub there is no impact.

Darth is partially correct you can have -15db sub trim (that is the lowest setting) without problem. The bug kicks in if you add in a 2-channel sub offset and the total trim is less then -15db. For instance you have a 2 channel offset of -2db and you change you sub trim from -13db to -14db the bug kicks in. The work around is simple turn down the sub amp gain so the trim attenuation is not near the max attenuation (-15db).

I installed the update Friday night, and it went well only taking about a half hour. I am happy to report that I no longer hear high frequencies from my sub when in stereo mode.

I will have a LFM-1 sub because I am ordering the 990/7125/LFM-1 combo.

Just set it up properly and you'll be fine. I'm sure Outlaw never thought of anyone neededing a -13 of sub trim.

I disagree it is a nasty bug and it is quite easy to get to -15db now that the two-channel offset "works", especially if you have lots of headroom with your sub. The simple fact that several people have stumbled on to this bug is proof enough that it needs fixing. Yes it is easy to work around using your subs gain but at the same time it is also easy to encounter the bug by using the 2 channel sub offset.

You should set your sub level at 0 then adjust the gain on the SUB to where you need it. Then fine tune with the Outlaw. You shouldn't have to go more than +/- 3db on the Outlaw, then you have your 2 channel trim to further tweak it in stereo.

I plan on purchasing my 990 in the next few weeks. Will this new firmware upgrade be preinstalled in forthcoming shipments?

I think one thing possibly missing here is that my sub gain was fine with the previous FW. I wonder if the defaults levels changed? I could definitely see the auto-cal routine possibly adding in a big attenuation too. I think expecting all setups staying under -15db with with the now working two channel offset is unrealistic. As I said earlier several people have already stumbled upon it. It is easy to work around but when it hits it has the potential to do damage to your sub, not a good thing.