UPDATE ==> IT WILL BE FIXED ON APRIL 2012 CU FOR SPS 2010 AND ON JUNE 2012 for MOSS 2007
I would like to inform that MOSS 2007 and SPS 2010 output cache stops working after installing security update for the .NET MS11-100 KB2656362 http://support.microsoft.com/kb/2656362 and KB2656352 http://support.microsoft.com/kb/2656352 . It is reported and the Product Group is working on a fix.
Please, it’s recommended from your side to measure if you want cache on the environment but to be impacted by security issues or to be secure but without any output cache.
Héctor Calvarro Martín. SharePoint Dev. Microsoft Support Engineer for DEV EMEA
On Spanish available in the Spanish SharePoint Support Team Blog