The best place to look for up-to-the-minute information on the Mars Rovers is Spaceflight Now's site. Lots of links to pictures, all the latest news.
The Spirit team have done a great job of remote diagnosing of the problems that rover has had. Basically, it's a hardware problem in a segment of the memory, the so-called "Flash RAM". This is a bit like the BIOS on your computer (assuming you're using a Wintel box), inasmuch as it's memory that's always readable, but only writeable under special conditions. It retains its contents even if the machine is switched off. (To Computer Geeks out there, please cut me some slack with this gross simplification, OK?).
Anyway, Spirit's Flash Ram is broken. She's a no-work, Luigi. Or rather, it nearly works, or most of it does, anyway. Hence the periodic resets, when the data from the broken section is read - it's corrupted.
Now fortunately, one of the many ways of operating Spirit is to use normal RAM instead of Flash RAM. Fedsat had the same properties, it could "Boot" in any of 3 different ways - from the Flash RAM, from the Mass Memory Unit (normal RAM), or via direct commands from the ground. It's a fairly standard way of doing things in Spaceflight Software.
So the Spirit is off the Critical list, and after a few weeks of rest and recuperation (and re-programming), will be back in full working order. Now that Opportunity has landed, and is in good shape, we'll see if it was a one-off or a systemic problem that will plague that rover too. But if so, no matter. It's being fixed.