Help with logging into my MacBook -it suddenly went into Safe Boot mode and it seems caps lock is activated

MaNuMaTeS,

which model MacBook Pro do you have, and which version of OS X is installed on it?

MaNuMaTeS,

boot your MacBook Pro into Recovery mode by holding down a Command key and the R key as it starts up. Once the Mac OS X Utilities menu appears, select Disk Utility. On the left-hand side of the Disk Utility window, select your internal disk’s boot partition (typically called “Macintosh HD”). On the right-hand side, press the Verify Disk button if it’s not greyed out; if it is greyed out, or if it reports that errors were found, press the Repair Disk button. Once the verification/repair is completed, exit Disk Utility and select Restart from the Apple menu to restart in normal mode. Does it still reboot by itself into Safe mode and activate your Caps Lock?

MaNuMaTeS,

boot into Recovery mode again and from the Mac OS X Utilities menu, select Reïnstall Mac OS X. Follow the instructions there, and when you’ve restarted, see if it safe boots again with Caps locked.

If it still misbehaves after the OS reïnstallation, then try the “nuclear” option of a clean OS reïnstallation. Back up your valuable data, then boot into Recovery mode again; select Disk Utility, and use it to erase the entire internal disk. Once it’s been erased, shut down. When you start it up again, OS X Internet Recovery will redownload and reïnstall your MacBook Pro’s original factory-installed version of OS X (viz Lion) from Apple’s servers. When Lion has been reïnstalled, run Software Update to get it to 10.7.5, and see if it behaves itself. If so, you might want to make a Time Machine backup, to give yourself a known good restoration point. You can then redownload and reïnstall Mavericks, and run Software Update again to get back to 10.9.1. If everything’s still OK, make another Time Machine backup as another functional restoration point. You can then restore your valuable data.

If it still acts troublesome after the clean installation, then it could be indicative of a hardware problem such as a logic board fault, and you should take it to an Apple store or other qualified repair facility.

MaNuMaTeS,

do you have an external bootable drive which you could boot from, to allow its Disk Utility to fully erase your internal disk?

MaNuMaTeS,

if you have access to a second Mac, it would be easier if you could purchase a FireWire 800 cable — then you could boot your MacBook Pro in Target Disk mode, so that the other Mac could treat it as an external drive to erase. (This would depend upon the other Mac also having a FireWire 800 port.)

Otherwise, if you prefer the external bootable drive option, and your external drive has been formatted for Macs, you could do so with just your MacBook Pro. Boot into Recovery mode; when the Mac OS X Utilities menu appears, connect your external drive, and then select Reïnstall Mac OS X from the menu. When it asks you which drive you’d like to install Mavericks onto, select the external drive. When it reaches the end of the installation, and it prepares to restart, make sure to disconnect the external drive as soon as the display goes dark, so that it boots from the internal drive rather than the external drive. Once it’s at the login screen, you can reconnect the external drive, log in, and immediately restart, holding down the Option key this time so that you can pick the external drive to boot from. Run Software Update to get Mavericks on the external drive up to date, and then run Disk Utility to erase the internal drive.

MaNuMaTeS,

at this point it seems like a hardware problem of some sort. Have you tried running the Apple Hardware Test yet, to see if it can detect a problem? (Note that if the Apple Hardware Test doesn’t detect anything, Apple stores have more thorough diagnostic tests available.)

Try booting from the external drive again, and use it for the same tasks that you would normally do when booted from the internal disk. If the external disk behaves itself, then that would suggest that the problem lies either with the internal disk or the internal SATA cable. If the external disk also turns up with a Safe boot screen, then that would suggest a problem with the logic board.