I'm getting the same error, and am unsure how to proceed. I did not download anything separate, merely followed the instructions on the main page. When loading parted magic I tried all three options at the top of the box with the same results. I tried it on another computer and got the same result
Setting up system devices... DONE
Searching for PMAGIC_2013_08_01.SQFS...
The PMAGIC_2013_08_01.SQFS file could not be found. Report this incident to the forum and if possible attach a directory listing of the Media.
mount /def/sr0 /mnt
ls -lR /mnt
At least report the full path and name (including upper and lower case)
or the absense of any pmagic sqfs files.
You are now on the command line.
Commands like "ls", "cat", and "more" are at your disposal.
Use <Shift+PageUp/Down> to scroll up and down.
When done type "exit" to reoot the system.
I have no idea what path you want reported, but it's a stock extracted ubcd.iso right off mirror one. I'll keep poking at it. I haven't used UBCD in years, but I don't remember it being this fussy to use. Maybe it's just rose colored memories.