Hmm, we have not heard of incompatibilities with these particular software, but it is still possible. It can be Cisco VPN (though if it is I guess we’d heard about this before but we did not) or Odissey (most probably because I’ve never heard about this software). The only way to get the exact answer is uninstall each of these services and check if problem is gone.
For the cases when incompatibility raises you still have an option to use NDIS IM version of WinpkFilter. It is less convenient in installation but it should not conflict with any similar software by design. NDIS hook is widely used but we can guarantee only the compatibility with WinpkFilter derived solutions, other third-party drivers may break WinpkFilter functionality as it is noted on the product homepage.