Exported video not playing properly

I am working on a 1920x1080 HD video. I converted it from a direct from camera MTS (168 MB) to an MP4 using Sorensen Squeeze (12 MB). Then in After Effects I used keylight to remove the background green screen and synched audio. When I exported the file out as an AVI (because I wanted the most loseless format for editing in Premier) and played the file the audio seemed to run fine but the video was running extremely slow and randomly stopping (the FLV was 8mb). I have double-checked that I am running 24 FPS on all versions of this video throughout the conversion process.

My question is whether the lag time in the export would be more due to the large file size and a lack of processing power (only running 4 GB of RAM) or if I missing something in my encoding/ converting processes. I have not previous had issues with encoding out an alpha flv. I know more information may be needed, but, as I am somewhat new to this, please bear with me. Thanks for any assistance.

I had a feeling it was something like that, but I thought it was odd that it wasn't working corrrectly on my flv export either. And one thing that I did forget to mention was that I can't get it to run properly once imported or copied over via the dynamic link in Adobe Premier where I am processing my final edits. I will look over the links and see if that helps. Thanks