Won't take serial on the SM site?  
Just close down your browser and start again.
Seems if you made any error when entering the serial number or other info, this wrong info is cached in the browser... at least that's all I can think of.
I had this issue and could not get past the serial number entry until I restarted IE Explore.
Oh, another thing, some browsers, Chrome, Firefox etc, don't play nice with some web sites when entering serial numbers etc. So try IE instead.