The April 2012 CU is now available again from Microsoft: http://support.microsoft.com/kb/2598151.
Their reason for the recall that happened about a month ago:
“A recent, isolated issue was discovered in the SharePoint 2010 Products April 2012 Cumulative Update that could result in an HTTP 500 error when users delete objects to include documents, lists, and Webs and a new object is created using the same path where the original object remains in the Recycle Bin. […]This issue has been resolved in the revised packages.”
