I've just ran into the same issue - disconnecting the web_analytics profile from the virtual server fixed it. Not quite sure yet what caused it, but here are some details of my system, in case it helps anyone else;
- Just upgraded to v15.1.0.2 (no issues with the same configuration under v14.1.2.1)
- VS has an HTTP profile, as well as SSL offloading, and an iRule and Local Traffic Policy
- Another VS with a standard pool and no funky iRules/LTP's, but WITH web_analytics profile, did not show the same problem.
If I find out anything else, I'll update this post.