Litecoin wallet "Error loading blkindex.dat"

ah - ok B4coins - sudden power offs can cause the database to get its knickers in a twist.
It's a balance of performance and integrity of the database - so sometimes things like the index don't get flushed that quickly - esp when you're sync'ing up with the blockchain.

The quickest way to get up & running is to clean out the old database files and to re-download the blockchain again.

There's 2 ways to do this - as ltcbtc mentions you can backup the wallet to a safe location (so you don't lose your coins & tx) and reinstall the client - or you can wipe the database files and restart the client.

You're on Windows - so the wallet (wallet.dat) can usually be found:

C:\Documents and Settings\YourUserName\Application data\Litecoin (Windows XP) C:\Users\YourUserName\Appdata\Roaming\Litecoin (Windows Vista and 7) Copy the wallet.dat somewhere safe before you do anything else.

If you'd rather try to clean out the old files - you can delete everything apart from the wallet.dat & the litecoin.conf files. Then just start the client again.

Reinstalling, once you've made a backup of the wallet is simple through the Windows Add/Remove Programs tool.