I must admit though that I haven't tried using VSTi's in Premiere. I can't really see th need for using VST instruments in a video editor. I'll use an audio editor to create the audio track and then I only need to tweak the audio a little within the video.
I separate out my VST fx from instruments and only load the fx into Vegas 12 or Premiere CS5.5
Plugins sure are getting to be a management nightmare.
RTAS for PT 9 and younger
AAX 32 bit for PT 10
AAX 64 bit for PT11
VST 2 and 3 with 32 and 64 bit version
DX for Sonar and Sony software
All of these can exist on a single PC. Wow!