Firefox is automatically decreasing the system volume when playing media
everytime i load a site that has music/media on it (youtube etc) whilst i'm watching videos in mplayer, miro or vlc the system volume for that sound 'device' (in the windows 7 sound mixer) will be lowered
You may be having a problem with some extension or plugin that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?
Try to clear the Flash cookies and settings. Flash Local Storage - http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html
If that didn't help then try to delete the macromedia.com and #SharedObjects folders to reset all Flash cookies and settings. XP: C:\Documents and Settings\<user>\Application Data\Macromedia\Flash Player\ Vista: C:\Users\<user>\AppData\Roaming\Macromedia\Flash Player\
"Application Data" in XP/Win2K and "AppData" in Vista/Windows 7 are hidden folders, use %APPDATA% in the File name field. See also http://kb.mozillazine.org/Show_hidden_files_and_folders