weird behavior of USB port


I have a Beagleboard C4 and the USB had been worked without problems until
this point. I am afraid that it has a hardware defect.
I downloaded a new image (2012 jan) with 3.0.17 kernel.
If i connect a mouse or a keyboard, i got the following message:

[ 65.685058] hub 1-0:1.0: unable to enumerate USB device on port 2

and, the whole USB system is freezed here: no more events (connect/disconnect)
are detected. (other devices keep working)

If i connect a 4-port HUB (after reboot), got the following messages:

[ 76.786407] usb 1-2: new high speed USB device number 2 using ehci-omap
[ 76.945678] usb 1-2: New USB device found, idVendor=05e3, idProduct=0608
[ 76.945709] usb 1-2: New USB device strings: Mfr=0, Product=1,
[ 76.945739] usb 1-2: Product: USB2.0 Hub
[ 76.947814] hub 1-2:1.0: USB hub found
[ 76.950347] hub 1-2:1.0: 4 ports detected

If i connect any device (mouse, keyboard, pendrive, etc) to the HUB, got this

[ 108.426971] usb 1-2: USB disconnect, device number 2

and the USB system is also freezed here.

The most interesting thing is that if i connect a pendrive or ethernet card
_directly_ to the board, it works perfectly. It can be re-connected, without
any problems. But only one device can be used this way at a time.

I have measured the USB power voltage, there is no problem, even when it is in
"freezed" state.

I cannot imagine what could happen with my board, any help would be

György Kövesdi