You might have to boot into Single User Mode by holding down Apple-S after the bootup chime. Usuall once you enter this mode, there are instructions right before you're dropped into the prompt. Do you get these same instructions when it goes into the command line mode by itself? If so, follow the instructions given. If not, then type "reboot", hit return, and right after the bootup chime hold down Apple-S and follow the instructions once at the prompt.
doing a sesrch on previous posts i found some command lines to type in.
i booted up holding down apple s. i typed in the /sbin/fsck -fy command.it then brought up dialog saying that it had repaied some files on hard disk or something like that. i then typed in reboot. the blue boot screen appered but then after few seconds went back to the command line.
the strange thing is that when i power on laptop, a small folder with question mark icon briefly appers.i get the osx startup box then after a while it just goes to command line. any ides? do u think i need osx disks to restore?
worst thing is i really need it working.some friends and today startes staples2naples rally.need laptop 2 acess web to upload daily blogs etc....
Have you tried typing "exit" to see if it will continue onto the Finder? If it does get you to the Finder, go to System Prefs-->Startup Disk and make sure that the proper System folder is selected. Once that's set, reboot and see what happens.
Hopefully this will fix it. I Googled your situation online and couldn't come up wiht anything right off the bat.