Latest versions of udev have problems with in-kernel speedtouch driver. The driver is not using new firmware loading api used by new udev versions and tries to load it independetly. Udev and the driver are loading this firmware at the same time causing race-condition. The driver succeeds to load about once for 15 tries. I don't know exactly in which version the firmware loading api was introduced but I've tried with udev-103 and the driver was not working, then reverted to udev-094 and the driver works flawlessly.
The problem was mentioned on gentoo forums:
There is also some information here:
So maybe the speedtouch-usb should check which version of firmware is installed and require some of the older ones.
*** This bug has been marked as a duplicate of 147006 ***