Panther has a serial number? AFAIK, the serial number listed in the About this Mac dialog is the serial number of your computer, if that is what you are trying to use.
oh, and i called apple, they said it is a common error they've had with the site. the woman i talked to said to try it tomorrow and if it is still broke to go ahead and mail or fax in the form.
i omitted the dashes. i called them and they couldn't get it to work either. said they are still having problems with it. she said the best bet was just to fax or mail in the form. i did. all is well.
Damn, I don't think I am eligible for the £14 upgrade. I bought my mac back in September but it only just arrived on Saturday! Apple should upgrade you for free if you have bought a mac in the last 6 months!