After 24 continuous hours of testing with version 5.14.6 we were troubled to see the same problem of incomplete windows. The Pico software appeared to be still running, but acting very quirky. A quick call to Pico tech support (Sarah, I believe) yielded Mark's suggestion of turning off the graph fun...

I have just completed a data collection exercise of a temper furnace requring samples every 5 seconds for 27 hours and sometime after hour 15 we started experiencing this exact same problem (flaky graph window and incomplete icons in recorder window). More importantly, the data we saved is no good. ...