10.6 Aluminum iMac w/wireless keyboard and trackpad.
Working fine long-term, no recent change to the h/w or system software.
All of a sudden pointing started operating as if permanently in mouse-down state. In Finder, this means that the mouse would move around the last-selected object. It is impossible to put the object down and so impossible to operate the Mac. Restart doesn't help.
I turned off the wireless devices, replaced the wireless keyboard and trackpad with old, wired keyboard and mouse, and restarted. Normal operation was restored. Tried putting back the the keyboard, but pointing was disabled the instant I re-enabled Bluetooth. Now stuck permanently as if in mouse-up state, so impossible to operate. Fail.
Temporarily OK with wired keyboard and mouse. Ideas how to return the system to wireless keyboard and trackpad operation?