Doesn't seem like you're getting much feedback for this so I've registered to let you know my experience with this.
I had the same issue while building the image with windows7. I did not use UBUSB, I instead used the latest version of UBCD4WIN to build the project then used WinSetupFromUSB to create an XP/7 Install/UBCD4WIN/UBCD/Ubuntu USB Stick. I'm not sure if the procedure it uses to copy it to the USB is the same as what UBUSB uses but I think it would be more likely be caused by the building stage while in vista/7 than the method used to copy it to USB, but I could be wrong. I could burn a CD from my build to confirm, but I don't have any blanks available at the moment. pcuser, if you would like me to test, I can pick some up tomorrow and check.
Anyways, to the meat of the story, I'd like to confirm that copying R000000000001.clb from Windows7 to the USB solved this issue for me. Feel free to let me know if there's anything else you would like me to test on this issue.
Thank you all very much for the help, and a huge thanks to the devs for such an awesome tool!
This post has been edited by aikon: 14 August 2010 - 07:08 PM