Are you sure that the hang happens in BIOS and not during early Windows boot?
(edit: OK, it indeed is the BIOS, I have missed few posts when writing this)
If this is really the case, you must have hit a BIOS bug. It might be fixed in newer BIOS revisions (check changelogs at your motherboard vendor's website), but probably it isn't and the only hope to have the problem properly fixed is reporting it to the manufacturer.
It might be possible to mitigate the bug by disabling "Legacy USB" (or some similar-named option) in BIOS setup. This will either disable USB->PS/2 translation for dumb OSs which don't support USB, or make the BIOS completely ignore USB devices, including the ability to boot from flash drives or use an USB keyboard for BIOS setup.