Andre, Short version: Solved. The cause was AVer Trinity TV card. Long version: During various attempts I have realized that the kernel timer latency reported by LetencyMon is a bit on high side (cca 0,3- 0,4 ms) for the machine even at the idle state of PC (just services running, including Mediaoportal TV service => CPU cca 2%-3%. In “stall” of PC (=CPU > 50%) kernel latency exploded to hundreds of ms. Tried to disable various devices in device manager => no change. Then I started from scratch, physically unplugged all devices (idle kernel timer latency about 0,1 ms) and returned devices one by one. As I plugged the Aver TV card, latency increased to previous 0,3-0,4 ms in idle state. Here we go. No freezes so far. What is interesting: - the TV card generally worked – able to tune, watch… everything - the lockouts of CPU NEVER happened during use of the TV Card, always when doing something else, usually (not always) when some heavy USB data traffic occurs - device manager enable/disable the card doesn’t change anything on the performance The Aver TV card used to be weakest point from the very beginning of this PC (2 years ago), however I thought I solved it and it is OK. At the end it was not. Learning point: What a fool man can become seeing interesting piece of HW in the catalogue. Even from almost no name company from Taiwan… Thanks a lot for inspiration and … you know, it helps sometimes just to share the troubles with somebody THX!