Symbian accelerometer readings massively delayed to client application

Accelerometer readings to a CPU-intensive application are delayed by as much as 5 seconds on N8, 12 seconds on N97mini. Same program works perfectly responsively on N900. Responsiveness on Symbian is OK if (and only if) task switcher is displayed. Suggests perhaps the application is running at higher priority than the server thread, which is the wrong way round.