Well this morning I woke it from sleep by wiggling the mouse (which btw is USB not bluetooth, only my solar-powered Logitech keyboard is bluetooth) and I watched the airport turn on but it would not auto-connect to my network, as set. I did remove my network and re-added it as security = Any (Personal) yesterday; as I had re-added it as security = WAP2 Personal a few days earlier. These seemed to have reduced the problem to once-a-day (strange) but have not eliminated the problem.
Aismaiil - Since yesterday morning my Service Order is set at Wi-Fi, then Ethernet, then Firewire, then Bluetooth DUN, then Bluetooth PAN. So apparently this made no difference.
However I did make an interesting observation.
While the network was still not connected, I selected Sleep from the Apple menu and waited for everything to power down. When it was completely quiet, I used the POWER BUTTON to wake the computer instead of anything else. When the computer woke this time, the network was automatically reconnected.
Somebody else in this thread pointed out that this manner of waking the computer from sleep seems to work also.
I'll have to see if that will work every time.
Not a cause-solver by any means, but a circumvention of the problem if one can get into the habit.