I've periodically had Winamp refuse to load several 3rd party plugins AND generate a UAC prompt for no reason. Rebooting is the only way to fix it as I have absolutely no clue what causes it. It's just really freakin' strange when it happens.
I've had it some times where it prompts for UAC every boot up until I reinstall it. Doesn't seem to be any rhyme or reason behind it, but deleting/renaming elevator.exe and elevatorps.dll stops it from doing whatever it is trying to do. Then it only pops up UAC prompts when you go into specific options menus.
I use Wumpus OpenAL v1.0.0 (which I think is the latest) as my output and I often get that it can't open the output channel.
This is lessened slightly by having Winamp in a directory other than Program Files (x86)/Program Files.
All I have to do is to open another Winamp by using middle click on the Winamp pinned icon (which ALWAYS works) and then I close the one that complained about the error.