I tried out the batch converter and it worked on my side. Can you confirm that you are not uploading a too large archive? If not, can you please provide us with more details on the uploaded files, so that we can test an as close as possible scenario?
the Telerik team
Consider using RadControls for ASP.NET AJAX (built on top of the ASP.NET AJAX framework) as a replacement for the Telerik ASP.NET Classic controls, See the product support lifecycle here.