Apple ID authentication not working

Question

Last year, I changed my e-mail address to reflect my married name. My old Apple ID was my maiden name e-mail address (I'll call it KR for short), and my new Apple ID (KT for short) is my new e-mail address. I assume I must have just updated my e-mail address with my existing Apple ID account (and therefore changed my "Apple ID," since it's just my e-mail address), as opposed to creating an entirely new Apple ID account, though I can't remember for sure. Up until yesterday, the "merged" account (some things purchased under KR, some newer things under KT) worked fine, and all of it responded to the Apple ID and password for KT.
Suddenly, yesterday, when I tried to play movies that were purchased before my e-mail switch from iTunes on my computer , it said my computer wasn't authorized to play KR purchases, and asked for the password. (When I test my purchased music, some of which I know I purchased before I changed my e-mail address, this does not happen). I tried every conceivable password, and then clicked "Forgot." There are two options when you've forgotten your Apple ID password: have reset instructions e-mailed to you, or answer your security questions.
When I select the e-mail option, I don't receive an e-mail (either to my KR or my KT address--and I have checked my Spam folders). When I tried to answer my security questions, it first asks for your birthdate--and when I entered mine, it said it didn't match what Apple has on file. I've repeated this process two days in a row now.
Oddly, I can still stream these movies to my Apple TV--it doesn't ask me to re-authenticate there (but I'm afraid it's only a matter of time, since the Apple TV does occasionally, and seemingly randomly, ask me to re-enter my password). My problem is that I can't play them on my computer, and I'm effectively locked out of my KR account. It's not asking for re-authentication on music, nor for the two movies I've purchased since switching over to KT.
Why might I be locked out of the KR account (not receiving password e-mails and not accepting my date of birth), and how can I re-gain access to my movies? While I'm at it, I would like to merge the KR and KT accounts, so that everything falls under KT and I don't have these differentiated access problems in the future. Thanks so much in advance!

Answer 1

Hmmmm... would appear that you need to be actually logged in to enable the additional menu features.
Have you tried deletting the plists for MAS?
This page might help you out...
http://www.macobserver.com/tmo/answers/how_to_identify_and_fix_problems_with_the _mac_app_store
Failing that, I will have to throw this back to the forum to see if anyone else can advise further.
Let me know how you get on?
Thanks.