it won't give a more detailed message than 'not loaded' because it can get very messy very quickly trying to programatically determine why plug-ins (and their dependencies are not loaded, especially with 3rd party plug-ins).
if anything i'd guess at some issue with anti-virus/malware software on the machine messing with things (have seen that happen once before) which incorrectly altered the loading paths of the plug-ins which caused some plug-in load failures.
all i can suggest is making sure you're using v5.666 build 3516 (http://forums.winamp.com/showthread.php?t=374929#download) and the plug-in updates (http://forums.winamp.com/showthread.php?t=373755#updates) as well as using a current version of in_vgmstream (as there were some issues in the plug-in along with Winamp that the most recent Winamp and plug-in builds resolved).
any idea what plug-in is changing the 'input' node to 'input / xsf' ? (as never seen that before)
The new Vio_xSF plugins put their settings in their own special pages rather than clicking on the plugin and hitting the configure button. Infact if you try to hit the configure button on those plugins it just takes you to those pages.
As for antivirus, I run no active anti virus software. Only thing I run is a firewall...
rightio, where are they available from? (as i'm too far out of the loop when it comes to vgm plug-ins).
only other thing i can think off is somehow the OS (or something else in the system) got into a weird cache state which broke the library search functionality / loading. though agree it's very strange, lets hope the plug-in loading changes i'm making for the next Winamp release don't break anything with in_vgmstream and other ones with their dependent plug-ins.
vio_xsf can be found on this japanese Foobar2000 wiki.. I forgot the link to it though sadly... I've lost track in the plugins too because after awhile it seems none of them are updated anymore.
vgmstream just stops Winamp from actually loading entirely. if I remove one of the library dependencies for it, or even the plugin itself from the plugin folder, vgmstream doesn't load and Winamp starts up just fine.
I've tried re-installing Winamp and also re-downloading both the plugin and external DLLs after re-installing and Winamp and it still doesn't like the plugin :/
Right click the main window in Winamp and select the first option "Nullsoft Winamp Pro" and it comes up with an About Winamp window which tells you the current release and build :)
that information isn't guaranteed to be there for all client releases (though should be with anything in the last few years). otherwise you have to look at the winamp.exe file properties to find out the build number from the version string.
Infernus Animositas: if you've got build 3516 installed, make sure you also apply the plug-in updates from http://forums.winamp.com/showthread.php?t=373755#updates (which i posted earlier along with mentioning what the 'current' Winamp release is :) ).