I been running Spybot Off and on with Avast for awhile now anyways, maybe 4 or 5 years…I even had Spybot Portable on my USB for awhile and also Used PC tools Firewall with this combo and they worked Very well together…No they worked Awesome together…
I would do as suggested by the guys here though ON Searching for any previous Antivirus that could still have reminants left and or Firewalls…Also check if you have any old versions of Avast, and use the proper Uninstal tool for each from their websites…Also check your registry and delete any Old files, or versions…
I didn’t have any issues on my PC But just did a random searc for Avast… even though I updated from the Avast Update button…But found some avast 5 folders there So did an Uninstall of all Avast and did a clean Install of Avast 6, and to my surprise my Web Shield wasn’t working…To Make a long story short …I did a Right Click on C drive …Check Volume for errors …after the check was done rebooted and all shields were working…Not saying that this will work in your case…just sharing my Opinion…
Cheers and Safe Surfing!!!