640x480 only res available after f14 - f20 upgrade?

[Bruno Wolff III]

On Mon, Mar 17, 2014 at 21:21:57 +0000,
   Morgan Read <mstuff at read.org.nz> wrote:
>
>I'd really appreciate anybody pointing me in the right direction(s) - I
>suspect I've just not done something really straight forward as it seems
>very strange that this old HP ProLiant ML 150 and equally old Dell
>1703FP monitor combo which worked fine under f14 now doesn't under f20.

Does that monitor do EDID? If it doesn't or returns bogus information, that 
could be what is triggering the problem. In which case using an xorg.conf 
file to state the capabilities of your monitor might help.