- Some BIOS'es reshuffle bootorder. Check that Harddisk-USB is still first choise
- Some thumb drives are partitioned or come with proprietary software pre-installed (such as U3 for many Sandisk thumbs) that may cause problems when trying to boot from them. For these you should try:
Network not working
- If you have added a NIC, don't plug the network cable into the onboard NIC.