Call Capital One and ask the "credit decision dept" why you can't get their card. Ask them what it will take to get it. Then if no luck, hang up and call back. Lots of lenders are very helpful with this information and this dept. can actually over turn a denial. I just got my last card like that. 3 denials, called and said. What's it going to take? They said, ok and gave it to me. I was a bit pushy. They gave me a low credit line, but I know I can ask for increases in 6 months now that my foot is in the door.
I don't know what's up with my credit. Capital One, Providian, and Wamu have repeatedly denied me over a 10 year period. I've always had other cards. Maybe they don't like seeing competitor cards on our reports. I don't know. If I were you, I'd make a phone call between 9am and 4pm Eastern Time to Capital One and ask! Then if still not having luck send in a letter telling them why you want their card and how hard you are working for it and to make your credit better. I am still after the Wamu card, just because. It has been a thorn to me for many years. Now it's just a challenge! hehe. I always call and ask what can I change to qualify.