Hi from over here,
Are your dimensions changing to read only, or are you creating read only dimensions? (this is not ment to sound so deep man!)
It is possible that equations are effecting some of your dims, but what normally happens is that if you try to change one of those dims, it gives a message along the line of "this dimension is driven by another dim".
More often the message you described is witnessed by new users who attach dimensions to the model rather than dimensions in the sketch. Could this be the case? if so edit the original sketch and put the dimensions in here.
drop another reply if neither of these tips apply.
demojok