Hello,
I have the same problem two days ago. However, I had Microsoft Security Essentials (MSE) installed at the beginning when I bought my computer from Dell (Dec 2010) (I did not use McAfee) . Two days ago I ran backup to my network drive as usual and got the error message, but I noticed the MSE detected a threat from java. I decided to uninstall all the downloads within two days ago, and the most important was to run FULL SCAN from MSE. It catched 3 threats from java and removed them. After this, I ran backup again and it worked beautifully. I hope this experience will help someone when I post my response.
My computer is a Dell desktop, i-5, Windows 7 Ultimate, My network drive is Seagate connected to Linksys E3000.
Note 1: I regularly update MSE to the latest.
Note 2: I've gone through the so-called 'reparse points' and no success.
Note 3: The download ones that I uninstalled all came from Apple (please do not get me wrong that I don't like Apple. I just wanted to test in all circumstances.)
Exactly the same issue, and same solution: run Full scan in MSE (which finds some "malware" that is javea related) and uninstall java, then worked fine!