@davec51
Your description of the block of U rings a bell - I recall that happening in earlier versions. From memory, which means I don't have a URL reference, the typical solutions were to :
- check the MD5 sum of the downloaded iso for integrity (and re-download if necessary, as Blaze suggested),
- burn the CD/DVD as slowly as possible rather than using the burner's max or auto speed settings, and
- press F6 after the boot begins and choose the "nomodeset" option (or add that to the boot codes if that's the method that's offered)
As a guess : if the above gives you no joy, search for <your Dell model> and Ubuntu in your preferred search engine.