I'm no expert, but first of all try calling back and speaking with a different person. Sometimes you'll get a different answer. Have you looked at your credit report lately to make sure that everythings okay? Getting a new credit card isn't worth dealing with major identity issues.

As a data point/side note, I had a problem with my last set of apps as well. Turns out the system flagged me because my address is in the credit report as "Third St" while I entered "3rd St". So...it can be something stupid sometimes.