I've been having this same problem too! I know I haven't changed my password since the last time I bought something, and clearly I can sign in here, so I'm guessing it's something on the itunes side. For the record, when I was prompted to recover my password, I never received my password reset email either, so I guess I'm just stuck for now.
I received this email from Apple and this corrected the problem for me... I only had to reset the iTunes cache
1) Open iTunes
2) At the top menu, click File > Preferences (iTunes > Preferences on a Mac)
3) In the Preferences menu, click the Advanced tab
4) In the Advanced menu, you should see a button that says "Reset Cache". Please click this button.