I had BT3 on it before and had the same problem but after some googling I found a driver and stuck it in some folder which I can't remember atm and edited the syslinux.cfg like the thread said and it was working perfectly.

Today I just quick formatted my usb stick and then used unetbootin with BT4(final) on the same usb stick i had BT3(final) on and I noticed it didn't have the same folder directories and so I couldn't find anywhere to put the driver and the edited (assuming this would work the same way) syslinux.cfg.

I am a complete newbie in regards to linux so please don't tell me to do anything without explaining what/where/how