Actually, I've just noticed it's a perfect square. I imagine what may be happening is that Glidos is trying to create a surface larger than is necessarily permitted under the DirectX9 API. Some drivers may allow it, others not. That's a guess, but a reasonable one. I can't remember if I pass errors into the log file. There might be something.

Well, here is the psVoodoo log file if that will help out. The game image is showing a 1200x1080 area.

Wasn't sure what to put the file license as.

Apologies for double post but I just noticed something.
As Paul said, it's a perfect square and measuring the image in paint.net, it seems that Glidos is trying to use a 1600x1200 4x3 sub area but my TVs native res is 1920x1080.
Why this cuts off the right side I don't know but that may be key to the cause

Bringing this up again as there's a new discovery. If I enable 3D Anaglyph mode, Inhibit Mode Change works as normal. DIsabled, I get the cut-off right side.

Any more clues?