I've been following the instructions "Preparing Files for USB Memory Stick Booting" in the Ubuntu Official Documentation for 12.04, and I'm using the "Copying the files the flexible way" method.

I've prepared the memory stick as per instructions, booted from it OK, and the installation begins. When it gets to the step of looking for an installer ISO image, it finds my downloaded file ubuntu-12.04-desktop-i386.iso, accepts it, and attempts to read it. I get the error message:

There was a problem reading data from the CD-ROM ...

Retrys do not help. I know this is a good file because I've used it to burn a CD, and booted with that CD. I tried saving error logs, but that step failed also.

Any suggestions on how to proceed? Thanks.