There are many vectors of attack if you are not careful.
Do you have backups of your blockchain.info wallet? If so, where? Are they sent to your email? Are they stored on dropbox?
Do you have a complex and secure password? (AT LEAST 10 characters long, including uppercase, lowercase, numbers, and symbols, with no real words)
Have you imported any private keys or addresses into your wallet that were generated elsewhere?
Have you accessed your wallet from a mobile device or public computer?
How sure are you that you don't have any malware running on your computer?
Did you accidentally access a phishing website that was designed to look like a legitimate site but was actually run by hackers?
thanks for the rundown...
Backups were stored on Dropbox and email
Yes password is very secure multiple 16 chars
No imported keys or addresses
No haven't accessed wallet from anything but this win8 laptop
Last scan for malware was yesterday after a defender update. No issues reported.
Haven't accessed any phising sites that I'm aware of. I used Bitvisitor.com to get extra coin from their services. Wallet address included in URL