product key doesn't work

I just bought Norton Internet Security 5 for Mac.  I downloaded it and tried to install the 10.6 version.  Everything initially looks good (seems like the product downloaded fine, and I get a message telling me to restart).  I restart and get asked for a key.  I put in the product key and I get a message "invalid product key".  Also, in mynortonaccount.com it tells me I haven't activated my product yet.  What am I doing wrong?  

 

I've tried removing my old version and reinstalling, redownloading, putting in the serial number (that seemed dumb but I couldn't think of anything else).  

 

Thanks!