Hi Jed Horovitz,
This is a generic error thrown by the Flash module should something went wrong while the file was being uploaded. For example, it might happen when the user is trying to upload a file, whose size is larger than the maximum allowed by web.config. Could you please verify that this is not the case? The default size allowed by ASP.NET is 4mb. I suggest that you take a look at following help article
for more information on the topic.
the Telerik team