To second something that GuitarTrek says, if you are running X64 and 32 (as I sometimes do), you want to be sure your plugin folders don't get mixed up.
Your 32 bit host CAN'T EVEN SEE your 64 bit DLLs.
On the other hand, your 64 bit host can see both 32 bit and 64 bit DLLs (that is true of VST only as far as I know). So even though you have both, you may want to be sure your 64 bit DLLs are named differently than your 32 bit ones.
For example, Flibbertygibbit.dll would be your 32 bit one, and would reside someplace inside the Program Files (X86) ////Vstplugins folders.
And Flibbertygibbit_64.dll might be your 64 bit one and would reside in the plain old "program files" structures.
Your 32 bit host can't recognize the 64 bit plugin anyhow, but this naming convention would let your 64 bit host "see both". If you (or the installer) named them both the same, then your 64 bit host would only see one. Probably the first one in the Vstplugin folders search order.
...a nearly useless tidbit there, unless you move stuff around in your spare time between games.