Locking Dimensions

[djlauch]

I'm a newbie and am following the tutorial for the retail building downloaded for Revit 2008. I have been creating floors and tested the models connectivity by changing one structural grid line dimension. I have found that two of the floors I created did not move to reflect the change in grid dimension. When I go in to edit the floor and lock down the floor edge dimension to the respective grid line I get the error message that locking this dimension would overconstrain the sketch. I assume that this must mean that the floor edge is already constrained somewhere else in the model. I toggle through the show view button and it simply reveals the dimension I would like to lock in various model views. This floor was originally created by aligning the floor edge with the 2nd. floor below (which is locked to the grid line on the 2nd. floor plan).

I have searched the help section in Revit for an answer and nothing really explains what overconstraining is. I have also searched this forum and found an interesting thread on pinning vs. locking, but no real discussion about not being able to lock a dimension due to overconstraining the sketch.

Any suggestions as to why I am not able to lock these dimensions and why if they are already constrained, they don't move when I change the grid dimension.

Thanks for your help!