LMS Linear Equalizer Disabled (Simulink)

Hello,

In R2008b, in order to use the "LMS Linear Equalizer" under "Simulink > Blocksets & Toolboxes > Comm Blockset > Equalizers", I firstly type "Simulink" on the command window and then follow the order I mentioned above by clicking on the symbols. After clicking on the "LMS Linear Equalizer" symbol, a dialog box appears:

http://www.hhresim.com/pictures/68ffffa967c1a7d7c4715c9fa7245df3.jpg

But unfortunatelly, I can neither type any value into the textboxes, nor click on the checkboxes. All the fields on the dialog box are disabled. I will be glad if somebody tells me what the problem is. Thanks...