**Edit - 8080 is in that port list also and this should should address it as well**
Gents, I had this too, but resolved it. Not sure what the implication is for AVAST, but SickBeard (SB) is working great again.
FYI - the typical SB install runs on port 8081. I changed it to 8082 and it ran fine. The only change I made was update AVAST.
I found reference to 8081 in AVAST. Removed it, and now SB starts just fine and no issues.
1) Go to "Settings"
2) Go to "Troubleshooting"
3) Expand "Redirect Settings"
4) Under "WEB" look for 8081
5) Remove "8081"
6) Hit OK and wait about 2-3 minutes
I don't get it (why the redirect wont allow SB to start, but this is clearly a issue with AVAST 2014 not SB)