Having set up a 6601 card for measuring time-between-two-pulses and pulse train period continuously, I have always found that eventually these controls (under Visual basic 6.0)cease to produce events and that rebooting my computer is the only cure. They may run OK for minutes or hours, but they finally fail. I'm careful not to touch the mouse or keyboard, but that doesn't help. Has anyone experienced this? What could I try?