The problem is "fixed" by moving the OK, Cancel, etc. toolbar so it is now above the numeric input field. This change is enabled by default in 2013 sp5 and SW2014 which will be released in the near future. In 2013 SP4, you can also get the new UI by using a special registry key. If set, then behavior would show the Dimension dialog with the OK/Cancel/etc toolbar along the top edge so it cannot be obscured by the drop-down box which offers other recent inputs, formulas, globals, etc.
You can enable the changes in SW2013 SP4 by setting the following registry key:
'HKCU/Software/SolidWorks/SolidWorks 2013/General/Dimension Dialog Toolbar Above' = 1
Let me know if this works out for you.
That does indeed work. Thanks.