Recently I encountered an issue with the Raspberry Pi where the taskbar kept flashing on and off, perhaps once every second or so.
After much digging around on 'tinterweb', I found that the solution was to remove the following entry for alsa in the following file:
Removed the entry:
Saved the file, rebooted the Pi (I don't think the reboot is essential though) and all now works perfectly! Hope this helps you.