More than 20 in a grid unable to select

I have a workflow that brings back user information and I don't know the exact number of returns that causes this to break.  But, if there are 1 to < 15 you can select the line in the grid and everything works fine.  If there are more than 15 or so it will not let you select the user.  Has anyone else seen this or know of a fix?

Thanks in advance,

John