Quoted from pinballinreno:
Bad file or incompatible USB disk.
Weak connector on the USB cable.
I also have an early 7.5v system and had to replace the cable with a better one for similar reasons.
SSD in the game is probably good although some people have replaced them. Any 30gb one will work.
Use rufus instead of unetbootin.
Unetbootin sometimes doesnt make a good image.
Use a USB 2.0 flash drive.
4 gb or 8 gb works best.
Although I am having good results with Kingston se9 early USB 3.0 data traveler 8gb drives off amazon.
Based on JJP support, I have used 3 different USB stick (one wasn't compatible and didn't boot) but 2 gave me the same Kernel error. The machine did not come with USB extension cable so i have open the PC chassis and plug directly into the USB port at the back.
I have used both US and EU image burnt with both Rufus and Unetbootfin, getting same error with both software.
I am happy to try a 4th USB stick before thinking about swapping SSD... This? amazon.com link »
Red stick in picture