Disappearing act

An interesting weekend looms ahead. Yesterday, a client called our sales guy who then called our boss's boss who then called our boss who called our project leader who called us. They were having some issues with some piece of software we sent them. Really weird stuff, the application was experiencing auto-close syndrome. What happens is you could be doing some very very normal action and the application just disappears without warning. No exception, no message, nada.

The application communicates with a serial device through COM port and uses some old VB6 components through Interop. The serial communication is using Win32 API through Interop as well. From observation and multiple testing, the occurence appears to be linked to it's serial device communication. Everytime I do something to the application which causes it to refresh the screen at high rates eg dragging a window on top of the main application window very very fast, the COM port appears to get flooded. After a short while, the application just disappears. It's not even in the process list. =( I've searched high and low, thorough and thorough and I
can't find any information on this. I wonder if my search phrases are inaccurate? Hmm...

I found some articles hinting at Interop not being so user friendly however there was no clear label on the packaging stating 'Use with care. Functionality NOT guaranteed'. Anyone out there has an extra helping hand or ten to lend?

Time to work on this, so ciao.