Confirm Form Resubmission Issue

If you add items to your cart, view the cart and then press back on your browser you get the following error.

Confirm Form Resubmission

ERR_CACHE_MISS
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This webpage requires data that you entered earlier in order to be properly displayed. You can send this data again, but by doing so you will repeat any action this page previously performed.
Reload this webpage
Press the reload button to resubmit the data needed to load the page.

This only seems to have just started happening.

Other browsers say things like ‘Document Expired’

The issue doesnt affect Fireforx – it only affect Chrome and IE so far that I have tested.