Unable to boot USB

[marc]

Been trying to use PLOP to boot on two machines:

I burned a cdrom from the .iso file in the /pcmcia/ directory of 5.0.12

The first, an hp dv8000. Not that old, came with XP, runs Vista fine. However, there is no in-bios USB boot. Booting the CD, I get the PLOP menu for for the two hds, floppy, cdrom and USB. Attempting to boot USB, it finds and passes two devices with "NO HD" then on device 6, it locks up. Star field freezes, etc

Turn off, plug in PCMCIA card, plug USB into that card. Reboot and boot USB through PLOP, it passes over HOST 1 finding the two devices it passed over the first time. Then it finds HOST 2 and a device on port 1. Where it promptly freezes
Forcing USB1.1, locks up the computer with the UHCI driver.

Second machine, a very very very old IBM Thinkpad 600E. Boot the PCMCIA cdrom and it also freezes if the stick is in a USB 2.0 PCMCIA card (same as the one tried on the HP), however if I attempt it in the native USB 1.1 plug it will start loading the (isolinux) boot program, and then freeze randomly at some point during the boot of the actual intended system - sometimes even freezing on the multilevel isolinux menu, before actually loading a system.
Forcing USB1.1, mode 1 or 2, has no effect on the Thinkpad

The usb stick is 16gig, and works fine booting natively into two systems that are new enough to boot USB. It also works in the two older systems when an OS is running. I looked for but could not find any limit on booting with 16 gig sticks. Unfortunately I have nothing smaller to test with.

In all cases, the USB stick works in full OSes. Both machines run the last updated BIOS.

[marc]

Solved, sorta.

8 gig disk works on the HP. haven't touched the Touchpad yet.

The 16gig exclusion could be more obvious