> Thanks for your answer. > I observe this happening is way random. > It only occur 1 or 2 times for day (in 8 - 10 hours).
Random is not good. It means it's very hard to track down. If it is important to you to try to understand this, then you will need to find the exact. repeatable cirumstances that cause it. That could take signficant effort and you may decide that once or twice a day is not worth it. My guess is some interaction with another program on your system that only occurs after a certain sequence of events. If you are able to isolate the circumstances, possibly you can see a way to avoid them happening. I am afraid I cannot provide any further input to on this
