I have to say I AM SORRY in advance in case this has been asked a million time already, and answered:

I had not opened my wallet in weeks, thought to do it in passing and it just sat there, for hours, not opening. I tried a few times, it wouldn't.
I deleted the various block files and let it download it again, yay, it worked! but then today I came down and the entire system was locked up so I had to reboot, when I tried the wallet again, same crap, though, it gave me an error about failure to load some block file (I forget the exact language), so I deleted the shit again and am now waiting for another days worth of the wallet downloadingthe entire chain.

Is there any way to avoid this shit???