After 15 min. of inspecting logs i found fix for USB Mass Storage on Gingerbread builds. They changed some interfaces in volume manager (vold), so i prepared fixed version of vold.
Usage: BACKUP /system/bin/vold
copy fixed vold to /system/bin/
(adb push vold /system/bin )
- also check file permissions after pushing (best to set 777)
if your system is mounted as ro remount it by: mount -o remount,rw /system
EDIT: Forgot to mention to reboot phone after changing vold
USE IT AT YOUR OWN RISK !!!
IF U HAVE SOME PROBLEMS WITH THIS VOLD JUST REPLACE IT WITH BACKUP U MADE (u made backup, right ? )