So for some time now Firefox v26 one Windows 7 64-bit Pro has been having performance issues. If for example, I used the search bar for an item, then once at Google clicked a search filter like Images, the entire browser would lock up for about 5 seconds before unlocking and loading the page. For a while I've just been living with it. However, I noticed this issue cropping up on a forum I frequent as well. Finally, after using Google a lot for various searching and having to wait for my browser to lock and unlock I had enough and looked into it.
Ran Firefox in Safe Mode and the problem went away. I restarted the browser and proceeded to disable add-ons until only a few were left, and lo and behold, the culprit was Avast Online Security. Once I disabled that the problem disappeared, and with the other add-ons turned back on except it, the problem is still gone.
I would like to know why the add-on is causing this and if this is a know issue or if there is something that can be done, because I do like having it enabled, but I'm tired of the lag and won't use it anymore until it can be fixed.