Here are the significant changes and/or defect corrections that were made available in the 10/28/2011Constant Contact API release:
Setting accept header to empty casues 500 upon performing GET on events
A bug in the Events resource was causing a 500 error to be returned when performing a GET on /events. This has been corrected so that and empty accept header is allowed and returns the default XML format.
@ symbol in user name causes 400 error when doing a GET on Export Activity File Link
The @ symbol is an allowed character in Constant Contact user names, so this defect was corrected so that the GET on Export Activity File link no longer fails with a 400 error.
Version 2.1 of QuickBooks Info Transfer is available
This new version fixes several defects and also provides support for QB2011 and QB2012. See the related FAQ here.
Create a contact list without any Name element causing 500 error
The <Name> element is required for a POST to the contacts lists collection. A missing Name element should not generate a 500 error. This was corrected and a new error message "400: No valid Contact List Name found in entry content" is now returned.
UX responsiveness changes for oauth app
Previously the Constant Contact login page and the OAuth grant access page did not correctly respond to changes in the form factor of the displaying browser. This made these pages difficult to use, especially on mobile devices. These pages were re-styled so that they are responsive to changes in device form factor.