Fedor,
What else is going on on your maching when this occurs? If you reboot and launch no programs...does this still happen? Are you running a LabVIEW application at the time this happens? Do you have VLM??...or are you hosting a remote panel off of a VI? What version of LabVIEW do you have?
I did find one instance of this happening to a customer in our database...it was associated with a version 6.x of LabVIEW and a reinstall fixed the issue. We could not repeat it in house.
regards,
Brett Burger
Applications Engineer
National Instruments