Bootable USB distro disastro

The quest for a distro that could be booted off the USB flash drive took a turn for the worse.
While the first attempt failed, trying to get Knoppix to boot off the drive, the second attempt with DSL was successful. Partly because there was a specific tool to accomplish this task, and all I had to do was watch the process after launching it.
After booting with the flash drive I concluded that the GUI was too basic for my taste, and revisited pendrivelinux.com for more options.
Kubuntu was the next item on the list. This too I did as told, and here is where things went awry. After configuring the drive, on reboot, the system would not proceed beyond the POST beep. I would get the beep, then the system would crash. The only way to get the system to proceed after the post beep was to remove the thumb drive.
I tried checking whether the contents of the drive were lost, but no the partitions were there as was the data. I tried deleting the partition, but that too did not improve the situation.
I am guessing that the Flash drive's boot sector has been damaged, but even in that case how could it crash the system - even without being able to access the BIOS to check if altering any settings would help.
Fiddling some more with hope.