Cannot boot from USB disk with "not a COM32R image" error

I recently had this problem and I solved it this way:

• hit "TAB": the installer will show a list of possible images
• type the correct image name (watch caps!)
• hit enter

I recently had this problem myself. My understanding is that the error has to do with a mismatch of syslinux versions (I don't know why or how).

What worked for me was deleting the vesamenu.c32 file on the USB drive, and replacing it with the most recent local version (located at /usr/lib/syslinux).