My unibody macbook 13" late 2008 keyboard was spoiled with water for a while. Result was a failure of a part of the keyboard. After securely drying and cleaning most of the keys started working again except 1 key >> the left shift-key stays permanently in Uppercase mode and isn't working anymore. This failure resulted in booting only in security mode (holding down the shift-key forces a Mac to boot up in security mode!). To bypass this and boot in normal mode I have to hold down the esc-key during start up until apple logo shows up. With KeyRemap utility I have to disable the left-shift key in order eliminate Uppercase. In my case the security boot is a keyboard problem.