Nope - I have the same problem and a reboot (several actually) haven't helped. I'm pretty sure some app has glommed onto teh button for it's own uses but how to find that out? Surely there's a master location to reset/choose functionality for this softbutton? I found the setting for double-click, so how about single click?
I'm not sure if there is a way around the issue you're experiencing as I haven't seen it here with my Bell Canada model Atrix, but I can tell you one thing for sure - a factory reset wipes the phone clean as a newborn baby's bum.
Seriously, I always do a factory reset shortly after buying a new phone. Why you ask? Simple I say. To wipe it clean and reset it back to original factory settings.
Even though your phone is new and hasn't had anything installed or altered, all phones are "tested" by Quality Assurance Personnel prior to being shipped out from the factory. In some instances, it was not reset at the factory by these personnel, or it was never fully tested, or it was dropped on the anti-static mat below the QA person, and replaced on the desk without any physical issues.
So I always do a factory reset shortly after testing the functionality of the phone to get back to "square one" and set it up the way I want.
Having said that, it's possible a "rogue app" has done something to your phone (read: memory leak or other) and caused issues. If you don't mind doing so, a factory reset will reset the firmware and give you a "like new" configuration that you can setup again. It's a hassle I know, but it gets rid of any issues/software that may be causing your problems. Then you install ONE app at a time, test, and then install the next app, until you find the culprit. Again, I know it's a hassle, but it's the price we pay for an open OS and lots of free Android apps.
PS - I've reset my brand spanking new Bell Atrix about 4 times since I brought it home. I setup, test, install apps, test, configure, test, and reset. I'm a geek I know, but I'm also very meticulous with my stuff, and that includes my wife.
PPS - don't tell her I said that, or she'll get REALLY excited and I won't sleep for days.
Yup, that's right...I'm still hopelessly in love with my honey.