Either follow this forum tutorial- Reset the Notification Area Icons Cache
Or using CCleaner, in the Windows tab check the setting Tray Notification Cache under Advanced and run CCleaner (uncheck when finished).
Both will reset the cache, fix any corrupt icons, and clear any old ones from the list.
Once you've done either/or above, restart Explorer.exe by typing "TSKILL EXPLORER" *without the quotes* in the start/search box and hit return.
You will have to reset your tray icon preferences though everything should be working correctly again.