Hmm, I am sorry to keep you busy like this, and dont feel obliged to make the changes. The program works as it is, but I have one more observation.
When I first tried your latest version, I thought there was still some problem with selecting songs, but I then did some testing with Windows Explorer, and it does the same thing, so I think it is actually a winamp bug. The problem is that if you have winamp in non-enqueue mode and double click a song, it is supposed to replace the current playlist with the new song. If, however, you double click another song too quickly, it actually enqueues that song rather than replace. I have only tried this on my system, but with both winamp 2.78 and 2.80. I am running win2k on a 800MHz machine. So this is not a problem with your program, but with winamp.
The latest thing I have noticed though, is that if winamp is not already running, and you double click a song in Music Search, it opens winamp, but not the main window. The playlist window and the EQ are shown, but the main winamp window does not show up. I can close both the playlist and EQ windows, but then I have winamp playing with no way to access it. There is no taskbar button. I can hear the music playing, but there is no other indication of winamp running. I can shut it down with task manager, but an easier method is to start winamp. The winamp main window then appears as normal, and the song that was playing continues playing. I can then close that winamp window and the music stops.
It seems like you are somehow starting winamp minimized, but in a nonstandard way, as the EQ and playlist still show up, just not the main window. As I said, this can all be avoided by starting winamp first, and then using Music Search.