I remember a friend having the a-m-v.org app installed and avisynth installed seperately creating two different install locations for it. It only loaded plugins from one of them though and we spent an hour trying to figure it out till I asked about it. You might want to make sure you didn't install it twice. If you have a plugin loading and working that isnt in your plugins folder than that would lead me to believe you have another plugins folder being loaded from another install directory or your autoloading directory location is somewhere your unaware of. I'd tell you how you can check but someone would probably be in shortly to raise hell about even checking the registry yet alone changing it.
"The people cannot be [...] always, well informed. The part which is wrong will be discontented, in proportion to [...] the facts they misconceive. If they remain quiet under such misconceptions, it is lethargy, the forerunner of death to public liberty. What country can preserve its liberties, if it's rulers are not warned [...] that this people preserve the spirit of resistance? The tree of liberty must be refreshed from time to time, with the blood of patriots and tyrants."-Thomas Jefferson