I have been having a strange problem with Adobe Flash in Firefox. Any time a Flash Settings Dialog box appears (ie: giving permission for a site to use your web-cam) I was unable to select a permission or tab. After researching a bit, I found that this is a prevalent bug that has yet to be corrected. The only work-around I have found is the following:
Go to Adobe’s Flash Player settings website:
http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager06.html
Once there, you will see the Adobe Flash Player Settings Manager. There are five selectable tabs on top. Select the tab that is giving you issues. For example, I needed to enable my web-cam on a particular site, so I selected the Camera/Mic tab. Once there, scroll through the websites in the list towards the bottom to find the site you want to enable your settings on. Select the “Always Allow” bubble. Flash should now work on that particular website. Alternatively, you can select the “Global” tab and allow all sites to access your web-cam/mic/storage, but please remember that this may compromise your personal security.