Can you please clarify how you test your case? Do you use Visual studio only or you test it after deploying on the server? In case you observe the issue when testing it in VS (under Cassini), I would recommend that you implement your test after you deploy it on the server. Please take a look at the following help article where you can find some more information on the known limitations with the progress area - RadProgressArea Known Limitations
. In general you should not encounter such issues related to the progress area when you try to cancel uploading a file. In case you still encounter it however, I would recommend that you send us a support ticket with a very simplified runnable project that we can test locally and help you out (I would also like to ask you to clarify the version of the controls that you are using).
the Telerik team
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