"Hang" and "Thinking forever" are not how I would define the term "latency".
You have described a breakdown in communication. You have also asked how to diagnose it.
I would look for a root cause by first determining what those "links" are that you describe, to determine what they do. HTTP? URLs? Javascript code? Java applet execution? Lotus Notes URIs? FTP URLs? Gopher?..... "Link" is too generic, ain''t it?
If and only if you have determined that you do, indeed, have a networking problem, instead of an application problem, then you can move to Step 3, above. One exception: if these are FTP URLs which fail for you and your users, I would look to your PF configuration once more. See the PF Users Guide chapter on
Issues with FTP.