2000 Lasabre custom 133,000 miles.
Please be patient with the details.
Symptoms:
This began a couple of weeks ago when my wife called and said the car would not start and the power system(locks etc) and lights would not work -except for the security light which stayed on. So I drive an hour and hooked up jumper cables and it fired up, with everthing working except the instrument cluster/panel lights and the under hood light. The instrument panel lights have not illumated since about a week prior to the beginning of the no starts. Just to mention a month or so prior to that the cruise control stopped working.
The next day I tested the battery(it is good), cleaned connections, checked grounds to body, fuse panel etc. Followed manual to retrieve unlock codes from radio with no luck! No problem for 48 hours and she calls again with same problem. I go down and check it out and try to jump it with no luck-so we leave it. The next morning I drive her to work and the car starts fine.
The car has been setting for a few days now with only 1 no start occurance. When it was running the radio, instrument panel lights, fuel and temp gauge would not work and sometimes it would.
Update June 22: Car started around 6 pm so I took it for a drive around the farm to see what happens.
1- Messages in dash panel
A-airbag, service engine soon, traction off, note these have ever appeared also security
2- What did not work
A- Radio, Trunk release button, power locks, A/C (the blower did), Fuel and thermo gauges, Radio, instrument panel lights

So I cut it off and it did restart, the only exception was th service engine light was gone.

Any direction would be appreciated.

Michael