For windows xp (home or pro) 256MB is barely enough to run the OS itself!
In our 6+ years of shipping Microstudio, and 2 years of Hoster, I have never heard anyone have to power-down to shut them down. Tiven the problem appears to be uniqe to your system, I'm "suspecting" it is your computer, not the software. The fact that your other programs can't continue or shut down is even more baffling.
Our software is developed using Microsoft's development tools. Our programmers are expert in Windows development, so I can't imagine there is anything we are doing that would cause this. It is baffling! I hope we can find a solution quickily for you.