Solved: Lenovo B590 wont boot from usb key

I've just bought this laptop, and it came with windows 8 preinstalled, and I'm trying to install Windows 7 on it.

I have a bootable usb, which I've used many times to install Windows on my other laptops, but the B590 just wont do it. I feel like I've tried everything. I changed the boot priority order in BIOS with USB HDD as number 1 but it still just boots into windows 8.

I've tried removing everything but USB devices from the boot order, and now I get this boot menu:
http://i.imgur.com/1iV2iaW.jpg

Which is exactly what I want to boot from, but when I press enter to boot from the USB device, nothing happens. It's incredibly frustrating.

The USB device IS bootable with a primary partition. I've used these steps to make it bootable in DISKPART:
http://social.technet.microsoft.com/...usb-drive.aspx

After having no luck on the B590, I tried booting on the USB on a different computer, and it works perfectly well. Starts installing windows 7. So it seems like the problem is not with my usb device.

I even tried restoring the USB drive and using Lenovo Bootable Generator application to make the usb bootable, with the same result.

Can anyone help?