error], how can i get pass this?

I have this error, and basicly what i wanted to do is to make a tank that can train a peon...i dont know why, just wondering if i could, but i geuss it checks to see if the unit that creates the peon is a building or not...and since it isnt...it crashes..ill try to emulate it later and show yo guys my progress.
[Noxz]

Several others have encountered this problem, myself included. I didn't really need it, so never bothered with a solution, but here are possibilities:
Make a custom unit based off of a building, then edit its stats and looks, especially movement, so that it can move. Perhaps an Ancient would be the best subject to use. If you use an Ancient, you may end having to root to train a peon, but it might work...