after:

echo shutdown > /sys/power/disk
echo disk > /sys/power/state

i get:

Could not suspend device 0000:00:0a.2: error -22

0000:00:0a.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 
1.1 Controller (rev 50)
0000:00:0a.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 
1.1 Controller (rev 50)
0000:00:0a.2 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 51)

it's a pci usb 2.0 card. no active device plugged there.

the bad thing is that i can't suspend.
the good thing is that kernel is safe, i can still work with it, without 
panic or other troubles.

i attach part of log.