Pete, increasing the "Time Interval between Traces" to 1000ms "cures" the problem. When the fault occurs the intervening slots show no data at all. I will mail a couple of jpg's directly to you showing the situation.<br><br>I am using a Win98 2nd Edition system and it appears to have problems with the 50 ms rate...Pentium II 266Mhz Compaq laptop with 96M RAM.<br><br>Hope this provides something to work with...maybe PP could back off if it detects something like this happening.<br><br>Cheers<br><br>Frank.<br><br>