VideoStudio :: X3 - Unable To Save Trimmed Videos?

This is my first use of Video Studio X3. My first aim is to simply split an mp4 video file into 6 parts. A simple thing to ask of fancy video editing software, right?

So I dragged the video file into the storyboard area. I used the "multi-trim video" feature and did the mark-in/mark-out thing and, seemingly, was successful in sub-dividing the original video into 6 smaller ones. Following the documentation, I selected "save trimmed videos" and get the error "The frame size (1440x1080) of the video file does not match the settings and therefore cannot be trimmed." (the original video is indeed 1440x1080)

Okay, fine. So I go to the settings, find the project properties, and discover that I cannot choose a frame size any larger than 720x480. Why can't I simply change the project settings to the necessary 1440x1080 frame size? The VideoStudio user guide is completely useless with any troubleshooting, as it gives the impression that the multi-trim video process is simple and flawless, as if nothing could possibly go wrong.