USB2 (EHCI) not working on my GA-MA790FX-DS5

[werdy]

I have a problem with my hacky. If I enable EHCI in bios (USB2) and make higher traffic on USB (copy from external drive, high speed mouse or webcam) the USB subsystem hang and every USB device stop working. If I reattach devices (plug out and in USB cabel) the system doesnt recognize it.

In USB1 mode (disabled EHCI) everything is OK but it is sloooooow (of course) and USB2 webcam is not working.

Is there any one with similar problem?

UPDATED: my memory is not so good, the motherboard is GA-MA-790x-DS4 (very similar).

My system:

AMD Phenom 8450
Gigabyte GA-MA790X-DS4 with SB600 chipset
4Gb memory
SATA HD and DVD