"The problem is mostly occuring when I connect to and after a short time disconnect the board from pc,"

Well, if your PC is not properly grounded, the PC chasis is at half the AC voltage. This is due to the type of filter used on main incoming AC power (isside the PC power supply). This AC potential ca, in some cases, ruin the devices connected to PC while PC is running.

Erik wrote:

"In his 09:10 reply to me he said so."

I can't understand why the webmaster can't assign serial numbers to posts under a particular thread. This would make easy to refer.