Is the monitor actually turning? or are you testing on your desktop PC?
Make sure the path to mrotate2 is correct in startcom.ini.
Do you have Mala V1.62 or greater? (I only have v1.62D, havent downloaded the latest yet, but I do plan to.)
try auto hiding the taskbar, it sure wouldnt hurt to try.
Startcom works great on my desktop PC. But when I moved it to my arcade PC I had to delete mala.ini and reset up mala before I could get mala to start. I tried removing startcom and got the same thing, so I think I screwed up my mala.ini playing around with the tree function a while back. Dont really think it was startcom related.
I do notice that on my arcade PC, when I rotate to vertical, quit the game, the screen is still horizontal, blanks out, then turns vertical. It doesnt do this when I switch from vert to horz. Quit horz game, when mala comes back it is horz, no visible flipping.
So I am aware of a small bug there, and that may be what you are seeing with your screen image. Although the kicker for me is that it works great on my desktop, which has an LCD monitor, the arcade has a CRT, but I wouldnt think that would matter.
Oh well, back to the drawing board.