I find the same problem with an image jpg and rerendering with a poll...
It works fine with IE 6.0 but not with IE 7.0 nor Firefox etc...
Do you find a solution, please?
Thanks for help
check fileUpload example. There is this cache problem solved by using f:param with timestamp in value.
This problem(client side cache, not server side) could not be solved within the component because if your value not changed browser do not get new resource but uses cache.