Don't know if anyone has come across this before. But if you have a usercontrol that uses VaryByParam and you have it on a page and do a postback you will get the wrong cache item. Use the below test bed to see what I mean, this is following to my post for help on the asp.net forums, I then found this...

Hey All, Had an issue today where I had a masterpage which was inherited from 2 pages. On the masterpage I had a control which is using output cache to cache the control. But ran into an issue where you would visit the first page say Test.aspx and you would see the control as expected, but then visit...