I can't imagine how you missed this from Adobe's "Contact" page:
CUSTOMER SERVICE BY PHONE
Check order status and get help with product registration, serial numbers, upgrades and other general questions.
Customer Service
800-833-6687
7 days a week
6am-8pm(Pacific time)
I had similar issues when I upgraded to CS3. Not all upgrade options are offered on the drop-down list and some Education (packaged) versions are not (single-program) upgradable. The only way to get registration authorization when it won't go through on your computer is to call Adobe. Once my registration numbers were verified, the Adobe customer service rep gave me a special access number. Each access number worked and all my CS3 upgrades work fine.