if you're saying that enabling this option on the Dells solves your issue, then you found the reason ;-)
It's to solve BIOS USB detection issues. Normally it should never be needed as the BIOS is meant to support PS2 emulation on USB HID's, but as you found, sometimes the BIOS doesn't do it's job properly.
Other BIOS's don't properly support protected mode interrupt sharing, so if you turn it on for those (like the unknown Toshiba mentioned in the original post) the machine won't boot any more.
Unfortunately for us, it's really hard to get people to tell us what machines they needed this option for.
Let's say we have an issue. I set this setting and make the system fail on bootup. Is there a way to reverse that setting (by Wintech/Safetech or any other tool) without removing and reinstalling Safeboot on the client side?
Tegsan, when new models are brought into our environment, our IT team gets them first, updates our image with the latest drivers, and tests encryption (for laptops anyway). You probably want to go through at least the same level of testing, if possible in your organization.