LookUp doesn't work in EP

Hello everyone!

I have a problem, what i think is simple to fix.

We have installed AX 4.0 and EP. When I create a Webform and Drag&Drop a Dimension Field like Dimension[3], then the LookUp doesn’t work in EP. I can see the lookup-button but by clicking on it, nothing happens. With all other fields with relations is all ok.

Also I programmed a lookup-method on the field, same… doesn’t help.

Is here a known problem with this? Or is it my fault?