Its not the key, it is the ignition switch. Do yourself a favor and buy the switch online,
http://cgi.ebay.com/ebaymotors/New-Porsche-Carrerra-996-Boxster-911-Ignition-Switch-OE_W0QQcmdZViewItemQQcategoryZ33576QQitemZ80737683 87QQrdZ1QQsspagenameZWDVW
Bring the part to your mechanic (or dealership) if you do not feel comfortable doing it yourself. I am 99% sure that is your problem, and it will solve all those symptoms you described. I had the same thing happen to mine i.e. windshield wipers, headlights, blower fan etc. Replaced it and everything is absolutely perfect. It cost me $250 I believe but I didn;t buy the part online. Hope this helps