Hey,
I'm sorry if this is already common knowledge but I've been searching and fiddling for the last hour trying to get my Action! recordings to work properly in Sony Vegas 12. ( Think it goes for all versions? ) The preview output was a garbled mess where you couldn't see what you were doing / editing when using an Action! recording.
Solution is to right-click the preview window and select "Video Preview Preferences" or the "Video" tab in options. Under 'GPU acceleration of video processing' set it to none as I believe in some cases, especially for Nvidia / CUDA users it will have selected a GPU per default.
With that off I can just drop in the raw recording and edit away, no problems.
Again, I do apologize if this is common knowledge but I figured I'd share it.