Why do my executables interack with one another?

[_K_]

I'm using two separate executables to control two different devices using serial ports (RS-232). The programs work great running simultaneously for hours... then, all of a sudden when a function is selected no command is sent and the machine locks up. I've also noticed that one program will hang up while transmitting automatic commands if the other front panel has been used last. It appears they are interacting. LabView 5.1, built on XP machine, running on 2000 Pro machine.
If anyone has a clue it would sure be appreciated.

[shoneill]

It may well be that you're executing both programs in the UI thread. This means that if they're in the same thread, they basically can't both be "running" at the same time.

Would it be possible to throw the instrument communication into a sub-VI executing in a different thread (Instrument IO for example)?

Hope this helps

shane.