Okay it looks like the reason you cannot click the link is that it is handled by Javascript. WWW::Mechanize does not interpret Javascript, you will have to do this yourself.

There is an (oft reffered to) thread on this which may be of some help How to handle javascript.

Also, just to make you aware, you may want to look at the Terms and Conditions on the site. I had a quick peek and noticed the following:

Unless otherwise specified hereunder, You may not sell, rent, modify, 
+reproduce, display, distribute, redistribute, republicize, retransmit
+, participate in the transfer or sale, create derivative works, or in
+ any way exploit or otherwise use the Site Content, in whole or in pa
+rt, in any way without the respective owner's prior written consent.
[download]

Pretty heavy huh?

Check out the Ethics of Webbots for some perlmonks opinions.