Same problem here, but mine started right after 10.6.5 was installed in November of 2010. My Apple Bluetooth Mighty Mouse and Apple Wireless Keyboard are no longer immediately connected after start-up. Sometimes it takes five minutes of trying and then they will finally connect. I have to use my track pad and go to the Bluetooth drop down menu and click connect, over and over and over. There used to be no delay whatsoever, they were just automatically connected after start-up. Here it is June of 2011 and this is still not fixed. This is getting really old.
About three years ago I remember doing an update and after that my Mighty Mouse would suddenly just lose connection while using it. Lots of other people had the same issue. It took Apple about 4 1/2 months to fix that one.
I do not understand why Apple allows these problems to continue to persist for so long. I have tried everything that has been mentioned in this thread to try and fix this. Nothing works. I have used Google and searched countless times trying to find a fix with no luck. Will Apple ever fix this??? What am I going to have to do to get this fixed? Buy a new computer?
I absolutely love Apple products and don't miss Windows at all, but I have gotten to where I almost don't want to install any of Apple's updates. Twice now it has messed up Bluetooth connectivity for months at a time with no end in sight this latest time. Thanks Apple.