Have just stumbled on this issue.
With just a usb2 keyboard attached to rear usb2 port [no/any hdd config], a single press of F2 when prompted will get bios - all good.
But, if I also attach my http://www.manufacturer.com/product/i44163-card+reader+-+AC-6000.html usb2 card reader to a rear usb2 port, it becomes a nightmare to get bios.
A single press of F2 when prompted does not work.
Multiple presses of F2 during the prompt does not work.
Single or multiple presses after the prompt does not work.
The only method that works is to repeatedly press F2 during the prompt and for at least one further press after the prompt has disappeared.
You can also just press and hold F2, but system beep protests because of buffer overflow, but it eventualy gets over it and all is well again and you have bios!
I understand that you are experiencing problems entering BIOS when you have a USB card reader connected to the motherboard.
In regards to your inquire, some USB devices may prevent other device to be properly recognized on your specific case I recommend you to use the back to BIOS button on the rear of the motherboard, pressing it will make your motherboard go in BIOS on the next boot. Another option will be to disable the boot from the USB device in BIOS, under the boot tab.
Hi PV, the problem still occurrs with usb boot disabled, in fact all boot options ex. cdrom and hdd are disabled.
It's not a big issue, I only mention it as it may be another piece in the puzzle of the other boot/hang issues. They may all have something in common.