black widow

i'm quite a novice user, but any help on this would be tremendously appreciated.

background/specs:
- mac mini, bought in january 2008
- 80 GB hard drive, about 15 GB used
- i think it's a 2.66 Ghz
- no idea how much RAM (sorry)
- i think i'm running 10.5 (or the latest version of 10.4)
- apple wireless mouse, apple wireless keyboard
- external lacie HD for backups
- pretty much use my computer for surfing, email and photo storage only

problem:
- i use firefox and 2 days ago, upgraded from 2.X (don't remember which version) to 3.0 from firefox.com

- after i d/l firefox, it created a volume disk icon on my desktop, in addition to the firefox icon i put in my dock. i couldn't delete the volume disk icon b/c it said firefox was in use, so i decided to just keep it there until the next time i rebooted or closed firefox.

- 3.0 ran slowly on my computer, i had issues with scrolling (either very slow or non-existent)

- also got 2 small pop ups today that i've never seen before, saying "[my user name] is unable to connect to the server". only option was to hit OK, so i did and computer seemed to be fine, although firefox was still slow

- decided to reboot. start-up process was normal: start up chimes, grey screen with apple logo, blank blue screen, desktop background with all icons and dock appearing.

- however, though i can move my mouse all over the desktop (replaced the batteries earlier this week, so i know that isn't the problem), anything i click on -- icons, menus and dock -- doesn't work. it's like the entire finder/desktop is frozen. (this is why i can't go into the apple menu and give you proper specs from 'about this mac'!)

- also, the trash folder automatically opened when the finder/desktop appeared. it contained 2 items: a jpg (which i put there) and a recovered files folder (which i did not). i was able to delete both of these through keyboard shortcuts, as they were not responsive to the mouse.

- in addition, the firefox volume disk icon disappeared from the desktop. the firefox icon in the dock turned into a ? icon.

- if i use the mac mini button to turn the computer off and then use it again to turn the computer back on after 10 seconds, it doesn't reboot from scratch like it normally would, it just shows me the frozen desktop again. so, i have used the button to turn the computer off, unplugged the power from the hard drive, waited 5 min, plugged the power back into the hard drive, rebooted and ... frozen desktop/finder, with the trash folder popping up instantly before i have a chance to close it.

- i tried again, same result. i tried again, holding down the combo to rezap the PRAM and i got the second set of chimes on start up, but ... frozen desktop/finder, with the trash folder popping up instantly again.

- here's the annoying part: the trash folder takes up almost the entire right half of my screen, blocking my hard drive icon. i can't go into my hard drive at all! i cannot resize, close or move the trash folder -- it's frozen.



i suspect this has something to do with firefox, as it was running just fine before the upgrade. it's incredibly frustrating b/c i can't access any menus or icons to try any diagnostics, but then again, i am unfortunately not much of a techie (zapping the PRAM is about the extent of my knowledge) and am absolutely terrified of wrecking my machine or losing my data (haven't backed up in about a week or so) if i even TRIED to run diagnostics.

any ideas? or should i just take it to an apple store and let them try to sort it out?

thanks!