I'm good now, but I should point out that I had the same random disconnects under SL. There certainly may be a problem under Lion, but the solution of powering off, and then pressing the power button on the keyboard for 10 seconds upon reboot worked for me.
There are other threads that discuss this. It seems thst there is a (temporary) probem with the blue tooth module. Once it is reset, all is well.
I thought originally that it was a bug in 10.7. Although it still could be, I think now that seems unlikely since there were so many Apple coders plus all the people working on developer seeds tjhat a generic boot-up/sleep problem with blue tooth wouild have surely been obvious. Any number of people would have powered off/slept their computers out of habit, security, transporting laptops, etc, that it's got to be an individual problem.
But admittedly, I still don't understand why I was good initially with a clean install, then had a kernel panic, then screwed, then fixed.
I'm sorry that I can't find, or give credit, to the individual that had the fix, but it's on these boards somewhere under BT keyboard/mouse problems.