Panicked quite a bit last night (and earlier this morning when iMac seemed to be stuck at the grey “Apple logo screen”, never getting to the login screen. And all this after a power trip at home!

Tried Techtool Pro – it reported the error, but couldn’t seem to fix it!

Thankfully came across a tip on using fsck in Terminal after booting up from OS X Install DVD

See this tip on Macoshints.com