There is scheduled maintenance for Intuit Payment Solutions on 11/12/11 from 8:30 pm to 1:00 am PST. According to the Intuit website, you will not be able to use the following services: Merchant Service for QuickBooks, Intuit Online Terminal, the Merchant Service Center, Go-Payment, and Intuit based E-Commerce sites.
You will be able to run voice-authorized credt card payments by calling the following numbers:
Visa/MC/Discover/Amex: 800-228-1122
American Express: 800-528-2121
Discover: 800-347-1111
For a full description of the workaround, click on this link:
http://www.quickbooksmerchantservice.com/newsletter/0905_Merchant_How-Tos.php