Intel cancels GE45, GS45, GM45 and PM45 stepping conversions
 

Previously planned to get new revisions, the GE45, GS45, GM45 and PM45 chipsets will have to make do with their current state as Intel has decided to cancel the their stepping conversions, without providing a reason for this.

http://www.tcmagazine.com/comments.php?id=24340&catid=2

Current oversupply of chipsets, perhaps? Intel has always released way to many chipset flavors, suspect they finally had to much oversupply and little interest. Especially with Lynnfield chipsets set to debut later this year.