While I find the built-in tools for creating bootable usb sticks from Porteus itself adequate, I have used the latest YUMI, which is very convenient at times.
I've used the UEFI-specific version of YUMI for 64 bit.
Supposedly YUMI "knows" about Porteus in it's supported distro list, but I'm not sure it picks up the porteus configs properly. Pressing "E" to view the configs shows a very bare minimum of config data. Maybe a YUMI fan can work with the author to see if there is a problem, or if it is just going by stale config info from 2009 or so....
Please reproduce your error on a second machine before posting, and check the error by running without saved changes or extra modules (See FAQ No. 13, "How to report a bug"). For unstable Porteus versions (alpha, beta, rc) please use the relevant thread in our "Development" section.