Rianna's friend has a great procedure for fixing it; I just did it myself in about an hour and a half! Stealership claimed that the HUD was a "factory-sealed module" that could not be repaired, only replaced, and that for $915...this after charging me $260 to completely dismantle the dash and put it back together again...I'm going to Jiffy Lube next time I need my oil changed, and every time after that.
But my HUD works now! And I did it myself, which is pretty awesome for someone who barely knows which end of a ratchet goes "ratch". (And I left a donation.)
Unfortunately, my story doesn't have a completely happy ending: http://www.flickr.com/photos/28516970@N07/3708963042/
(My dash panel had already cracked in several places, so this wasn't really a surprise. Pissed me off, though.)
*******
This is something that's probably going to happen to anyone with the HUD, sooner or later. The block where the spring attaches to the HUD housing is very soft plastic; I didn't even need a power drill to put a hole in it, I just used a pin vise. You could clearly see how the spring had sawn through the plastic. If you know people who have this HUD, this thread is a good thing to show them!