Electrical Problem

My buddy has a 2007 Toyota Tacoma v6 d/c. Some times when he turns off his truck,when he gets back in and turns it over he finds he loses all his radio pre-settings and his clock resets,etc.....His battery checks out ok along with his alt. Its like someone unhooks his battery cable and resets it again. Now this does not happen every time he gets in. It seems to happen after the truck sits over night. At one time he could not use his remote to unlock his doors. So he used his key and got in and noticed that the interior lights would not go on. Strange thing is he put his key in,the guages lit up and he was able to turn the truck over no problem. After it had started the lights worked and he was able to use his remote again. WTF is up with his truck?

 

Damn taco gremlins!!

My best guess would be a loose or corroded main ground, but even that sounds far-fetched. Anyone have access to a schematic by chance?