KVM causes hang on boot

I have three machines plugged into a Belkin Soho F1DS104L KVM switch. As a KVM switch, it has an onboard hub that connects the mouse/keyboard to each machine. If the USB cable for this is plugged in, the boxes will hang during startup immediately after "NET: Registered protocol family 1".

The boxes all PXE-boot off the network with Ubuntu 10.04 through 12.04 depending on the bootloader selection. All versions are affected. This also occurs using an Ubuntu 12.10 desktop image loaded from a USB drive.

As of right now, the easiest workaround is to unplug the USB cable while booting up. However, the machines aren't the most accessible and this partially defeats the purpose of the KVM. Are there any solutions for this? Should I submit a bug report? Thanks in advance.