When you go to the contact page and select the "vendor" option , you will see that you are not able to send them a message. Only a fax number...
Ripped, That link you gave , still requires that you are already a vendor, I want to ask a questions as non-vendor, prospective vendor...
Just ask here, They're getting thousands of e-mails daily probably, and will just respond with a generic e-mail template, reminding you to visit their help center. You can get real answers HERE.
Take Ripped advice. This is the fastest way to get answers from real people that is into affiliate marketing just like you.
Clickbank has been very good about answering my emails. You can pretty much send your question to any clickbank email address and it will eventually get forwarded to the right person. As for telephone numbers - I did talk to them on the phone once. There is a phone number on the tax documents they send out. I left a message and they called right back.