I've had a similair issue with 2 servers.. one 4.1.0, 260247 and one from 5.0. Updated the 5.0 machine to U2 but same issue happens.
LSUSB returns nothing.
./sbin/services.sh restart doesnt help either.
Removed and Adding the USB controlled with no luck. One thing to is a USB keyboard working in the BIOS but as soon as esxi loads.. the keyboard stops working and you are unable to get in to the local console on the server.
Tried a USB HDD and a USB memory key... no luck =\
Regards,
Adrian