Hi, when I investigated it further I found out that the unetbootin application didn't use the isolinux.cfg in the boot folder. It created it's own syslinux.cfg file in the root of the device. When I copied the isolinux.cfg file to syslinux.cfg in the root, everything worked! So this is a unetbootin bug! I have now run both coreplus and tinycore from USB thumbdrive successfully.
Thanks,
B-O