Itunes reset itself- authorized songs now unauth and says 5 of 5. why?

Question

i bought music from itunes store w/ a gift card from xmas. my power cord got accidentally unplugged and my laptop died. when i rebooted, my itunes had reset. i had to reimport the whole library, and now songs that were once authorized on my machine are now coming up that all 5 of 5 are authorized- even tho this machine is one of the 5!
somehow, in the mix, the first album i bought seems to have dissapeared (i have over 150 gigs of music, not sure what happened. just recently noticed it was gone). When i go to 'purchased music' it only remembers what i've bought since i had itunes crap itself and reset.
what gives?
itunes music purchasing really *** sometimes.
powerbook g4   Mac OS X (10.4.3)  

Answer 1

When you reach the limit of 5 authorisations you have the option once a year to deauthorise them all in one go and start over:
About iTunes Music Store Authorisation and Deauthorisation
http://docs.info.apple.com/article.html?artnum=93014
You can delete your "Purchased" playlist and create a new Smart Playlist and set as rule:
Kind - contains - protected
This playlist then will contain all your purchases and always will be up-to-date.
When you make a new purchase, your 'Purchased' playlist appears again, you can then add your previous purchased music to it.
Although the 'Purchased' playlist is a special one, it behaves like a normal playlist and you can in fact add and remove anything.