It's not dead yet!

Sounds like NASA has figured out what's wrong with Spirit, and should be able to get some level of functionality back. Apparently one of the Flash ROMS is bogus and booting from it causes the reboot loop. The press release mentions booting from RAM every morning so I guess they can work around it but have to keep an image in main RAM - which I imagine is a power drain. Maybe ultimately they can reflash the ROM and get the problem solved permanently.

That press release mentions that they don't expect to alter Opportunity's mission due to what happened to Spirit, which is also good news.