It's no secret that banks are much stricter when qualifying you for a loan to buy a new house. In the past, it was very typical for buyers to spend the intervening weeks before their closing shopping for furniture and appliances. This way they could close on the new property and have their new living room set and washer and dryer delivered the next day.
On June 1st, Fannie Mae started a new rule called Loan Quality Initiative. One of the requirements of these rules is for your bank to pull a last minute credit report. They're looking to see if you've incurred any new debt since your mortgage application. Wait until after the closing to purchase your new bedroom set or the widescreen TV you've always wanted. Don't apply for a new credit card or even a store charge card either.
Don't derail your closing - put your credit card away until after you are the owner of your new house.