Hey Hans... I'm using DSP on Station Playlist and something changed in a few recent versions that doesn't allow upgrading the plugin unless I fully exit out of Station Playlist. It had previously worked when disabling the plugin in the program settings and it closed out. Did something in the code in the installer for permissions change recently?
I have no idea what that could be. Do you remember when it broke exactly? Then I can look back in the change history. As far as I'm aware, this has never been possible, not even with version 1.0... At least not in Winamp; could there be a change in SPL itself?
(What has always worked - and still does work - is renaming the existing DLL to something else and then installing the new one).