It's the dirty little secret we all know about... sometimes... people fudge their dimensions.
The quick and dirty way to see is to invoke the DIMREASSOC Express Tool (or DIMREASSOCIATE, if you like typing out even longer words).
You can select all of the entities in the drawing, and dimreassoc will create a selection set of only those which have been changed, allowing you to see them more easily.
There are other routines available, such as this one over at CADTempo, that will place other visual indicators.
Anybody else have any favorite ways of easily detecting rogue dimensions?