Ok I got through. I had to create a yahoo mail account first instead of registering at
http://smallbusiness.yahoo.com/domains/.
My review so far from the domain i registered is the following:
1) Whois information automatically becomes what was entered on the credit card (name and billing address)
2) So far I am unable to enter the contact name in the whois (it remains the one used on the credit card and does not look editable)
Other than the little whois problem and taking 2 minutes to find out how to get to the control panel, it's worth the $4.95.