blank blue screen after logging in

so my friend has a macbook... he says it was working fine, he had added a few widgets, like the mlb scoreboard and weather channel something or other. he is "99 percent sure" he shut the computer down during an update-- but on the desktop he says...

and now every time he turns it on, and logs in with the right password it goes to the blue screen for a second, and then back to the log in window (believe me, he isnt putting the wrong password in, it shakes when it does that).

i tried disk utility mode to repair permissions
tried starting in safe mode
even use the fscw -y -f thing, or whatever it is to use single user mode (aka old skill disk utility)

so im wondering what my next step should be. Can i just restore factory settings or something? I dont want to have to completely reinstall...

thanks!

I am not sure what kind of update it was, he doesn't remember.

amiga said:

Could try an Anchive and install (last resort)... or start up in safe mode by holding hmmm is it shift or 's' I don't remember now. and see if you can sort it like that...

Or you could try resetting the PRAM or what ever it is.

Click to expand...

already tried booting into safe mode. I am trying to avoid a reinstall... but it may be what we have to do...

he said he was installing "like two things" - one of which was itunes.

sounds like we are gonna do a complete reinstall or an archive and install. Is there any way an archive and install wouldnt actually fix the problem?