Weird issue on some sites using Flash...

I have been chatting on a couple of sites based on 123 Flash Chat software. During the last week, I have been unable to scroll in any direction while in these sites. All of the other functions in the rooms work fine. I completely nuked Flash Player and reinstalled it - the problem is still there. Does anyone know what might be causing this problem?? It is really annoying to have to use the scroll bar instead of the mouse if I miss something.

I am on a Mac Pro running OS 10.10.2. Flash Player is up to date. Firefox is version 37.0.1. I am using the same extensions that I have always used - AdBlockPlus, Facebook Purity, Classic Theme Restorer, and FlashBlock (the chat sites are in the white list for this extension).

If anyone has any ideas, your input will be greatly appreciated.

P.S. One other problem is that when I try to use a keyboard shortcut when I am in one of the two chat windows to open a new window, it does nothing. If I go to another website window, the keyboard shortcut works just fine.

P.P.S. The problem still occurs in Safe Mode. I have also tried refreshing Firefox, but the problem persists. I prefer to use Firefox, but I may have to look at alternatives. Howver, Chrome does not see my iSight camera (external Firewire model) - all the other browsers see it just fine.

Opera scrambles the video from the camera. Safari runs the video just fine, but it tries to scroll the main web page when I try to scroll the chat discussion.

I have also discovered that the inability to open a new web page with a keyboard shortcut is present on some sites where I am viewing a video that requires Flash Player (it does not happen on YouTube).

This problem is beyond weird and very frustrating. Everything was working just fine until about 2 weeks ago. Are there any other troubleshooting options that I can try??