Hi Uwe,

Is the problem that I create and attach QwtPlotItems to QwtPlots within a worker thread? Do you do this? My intuition had been that calling replot from a worker thread could fail but just making the objects could be done anywhere. Otherwise, what you're saying sounds just like what I do, except that in your case the timer is in the main thread whereas in mine it's in the worker thread, which shouldn't make any difference.