Thanks for trying out the plugin and letting me know about this odd problem. I assume you are using version 1.2.0? I assume you are on the latest version of WordPress?
I have re-checked and the help tab works on my test site and a couple of client sites so there must be something about your setup. Hopefully we can work it out and I can develop a fix for you and anyone else seeing this.
I did notice that on my test sites and on my client sites the URL is different to the one you have posted. In your URLs you have .../admin.php?... but in the URL's on my site or my client sites it shows ..../edit.php?... and this works.
If I edit my URL ut use admin.php then I get the same problem you describe with the first link.
Interestingly, I don't set this part of the URL in my code as I use a relative link
href="?post_type=pgeek_sas&page=pg-sas&tab=help" and WordPress fills in the rest - so I will investigate why you are seeing admin.php and others are seeing edit.php
If you can give me any info on your WordPress setup that might be unusual then that would be great (you can email me direct from http://www.peoplesgeek.com/contact/ if it's info you don't want to make public)
Thanks for your help and thanks for reporting this problem.