is there an Activate Dimensions button in your options bar? if so, click that and you can modify them.

There's probably a Lock somewhere.
Either that Wall is Aligned and Locked to something else (another Wall or a Grid) or there's a Dimension with a Lock on it.
First select the Wall you want to move and look around at the Temporary Dimensions that show up. See if any of them have a closed Lock icon.
If you don't see anything there, click on the "Reveal Constraints" icon at the bottom of the drawing window. That should show you in maroon anything the Wall is constrained to. Unlock any closed Lock icons you see.

In general, you're going to get in trouble if you start Locking elements in a model. The motto in our office is "Locks are for Families, not Projects"
It may seem like a good idea at first, but you're pretty much guaranteed to run into the kind of problems you're seeing once you start locking down Walls.

That would do the trick. Thank you!

Is there a setting in the wall type that causes me to have to click "Activate Dimensions"?

My guess is that the dimension is attached to something that is co-planar with the wall, but not the wall itself (floor edge maybe?). In these cases, I'll re-dimension, but pay more attention to what item is identified on the status bar before setting my dimension.

Check to see if the wall is pinned. If it is, you cannot drive the wall with the dimension.