Anyone any ideas? if it was a remote desktop app certainly wasn't notified, does anyone know what to look for in the Task manager for suspicious apps?
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?