please fix invalid security code issue iPhone

Hi and welcome...
Since your geographical location in your profile is Toronto, check out the post here by:
Mobidoy You need to scroll down.
http://discussions.apple.com/thread.jspa?threadID=2435909&tstart=0
BTW. This is a user to user forum, not Apple. You can post feedback here if you want.
http://www.apple.com/feedback/iphone.html
Carolyn
27" iMac 3.2GHz i3 MBAir iPad iPhone 3GS 4.2 iLife iWork Pages Keynote Mac OS X (10.6.5) QTPro Intuos Tablet Epson Olympus Airport JBL

Hey man, not sure if you have had help with your issue yet but if not....
I had the exact same issue. I was given an ipod touch for christmas, and i was trying to download a free app and i was prompted with the invalid security code. Yet only a few minutes earlier i made purchases through itunes (on my mac) using the same card.I was having a conniption...
I called my credit card company, and it wanted me to confirm some payments. i did. And they were from itunes. I then went back to itunes, and looked into my purchase history, and it seemed that there was an error during downloading? I had a balance of $1.38 on my account. As if i downloaded a song but wasnt charged fast enough. Either way, i paid that debt off, and voila my security code was valid once again. As i was typing this i tried to find where the purchase history was, and im having some difficulty lol
If you can find it im sure it will fix your problem...
i hope..
Macbook Mac OS X (10.6.5) Ipod touch