a few weeks ago, my dad bought a new iMac. it works fine, except for the rare blue loading screen of eternity T_T anyway, i was up late last night and my dad told me to put the comp to sleep when i went to bed so he wouldn’t wake anyone with the startup noise when he got up to work. i went to bed at about 1:30 and put the computer to sleep. when my dad got up this morning (i was still in bed) he logged in and worked for a while. then, he logged out, and when he logged out, he saw the login screen background, but no login window 0_0 he kind of freaked out, restarted the computer… to the same screen T_T after loads of fiddling he somehow got logged in again, only to notice that he couldn’t click anything in his firefox window, and the top menu bar was gone. after loads more frustration and fiddling and doing random things he got it back to normal… so… does anybody have any idea what could be wrong???
Reset disk permissions
Repair your harddrive (Booting into safe mode automatically runs a disk repair)
Zap your PRAM
Although faster speaks the truth, I honestly doubt that will help you. It sounds like bad kernel issues (yes, osx has a kernel too! : P) alternatively bad physical RAM.
If he just bought it, It’s under warranty. Just take it back. No point in spending time with something you shouldn’t have to spend time with.
Yea true, if what I suggested doesn’t work, then what sekasi said is probably the actual problem
taking it in is your last resort
And people say Macs run perfectly! Psh. 
I’m adding this case to my repertoire of reasons why Macs are just as poopy (Insert other four-letters words there if you want.) as PCs.
Welcome to life, where anything that CAN break, DOES break
Zapping the PRAM and repairing permissions is not going to solve the issues listed.
It’s not going to hurt anything either though.
Reset the SMC.
This can mitigate many hardware initialization problems that arise during the process of updating the firmware, which has occurred at least twice in the past 6 months for iMacs)
This is essentially just shutting down, unplugging everything from the iMac (powercord last), plug everything back in(power cord first, IIRC) then restart.
Search apple.com for the detailed procedure.
Replace the RAM. Install the 4GB kit from OWC.
Do a clean installation of Leopard; wipe the disk.
GL
BTW, healthy Macs with sufficient RAM run perfectly.
