They claim an "extensive security threat" I would approach them in a polite and inquisitive manner and just play it dumb.
'oh geez, I'm so worried, what do you mean a security threat? was my identity stolen? should I file a police report? Did I do something wrong? why would someone steal my identity?"
playing dumb and the ID theft route might make them more lucid with giving out info as to WHY they had a red flag go up on you. You might not get anything out of them, and in the end they don't HAVE to grant you credit and can retract the offer of credit at anytime they wish - but usually honey attracts more bees than vinegar.
If you can't get anywhere with that number, I'd try contacting the Cap 1 exectuvie office (search for the CEO's email address) and just write an email saying "I was a loyal customer for ____, I used my card wisely, I didn't do anything that was risky or even would be considered questionable and yet capital one decided to close my account and not give me any info. I spoke with _____ and (s)he wasn't able to give me any reason. I feel singled out and manipulated. I've been trying to (re)build my credit and now I feel as though I've been taken advantage of by someone I had trusted to be a partner in my life long journey. Blah blah blah fulff fluff fluff, praise of Cap 1 follwed by how your now feeling like a common street whore...sincerly you.
You should get a response by someone...it may not open your account, but they may be able to tell you WHAT caused the red flag and why...heck they may even give you a CL on your other cards with them as an "im sorry"
Starting Score: 560
Starting Score: EQ 717 EX 724 TU 736
