Change in behavior of SharePoint Server 2010 Output Cache after April 2012 CU
You may remember that some time ago I published a web post regarding output cache stops working after installing MS11-110:
Like I pointed SharePoint 2010 April 2012 CU fixes that issue. The public info regarding that change has been publishing on the following KB:
I hope it will be useful for you.
Héctor Calvarro Martín. SharePoint Dev/Core. Microsoft Support Escalation Engineer for EMEA