I've had this problem with another Fujitsu Siemens computer as well, and I remember once back in the days that I had to inject drivers for some kind of SATA controller on my XP disc to be able to reinstall that, so I'm wondering if this could be related.
Although the problem I've had historically with the other FS computer is a little bit different, it always happens in the same place in the boot process. I have no problem choosing USB as the boot option and actually booting, getting to the Ubuntu selection menu and all that. It's when I choose to actually boot that it gets stuck. The same happens with Linux Mint, where I've tried the normal variant and the LXDE variant on both USB and CD.
Previously it has gotten stuck at the initramfs prompt, but here's an image of where it gets stuck now:
Does anyone have any experience with this and what kind of tweaking needs to be done to get Ubuntu to boot? I'm even open to hardware tweaking (i.e. removing some kind of unnecessary controller if any).
Thanks in advance!