Javier (and all) -- I saw your post and I was thinking that maybe, in some way, my development experience may help a little. Here is what happened to me recently. I build ASCX-based custom Modules with C# and they are simple to develop and quite stable, and I can do almost anything in them with pure C#. I was recently was trying to use a custom file uploader, specifically the ones from the AjaxControlToolkit. I should say I am working with DotNetNuke "8.0.3" as I cannot upgrade yet. Anyway, using those controls turned into a major horror show. It was extremely fragile and styling was near impossible. DLL references would break often, for no apparent reason. At least for me. Then, I tried several jQuery/JavaScript alternatives. No luck. Quirky. Hard to setup. Too much of a Ball Of Mud of JavaScript and jQuery and "related" files. So, I downgraded, and I went back to the pure "asp:fileupload" control and it works great-- not as robust or fancy as some other controls claim to be-- but it is very stable and cross-browser support seems good so far. The only caveat is that it uses the underlying HTML input type=file control, which is notoriously difficult to style so my solution was to add no style to it at all and use it out of the box and it does actually look (and work) well in IE, Edge, Chrome, FireFox, modern versions. So, for you, at least as an experiment to help you narrow down the issues, I would say write a test with the plain-vanilla "asp.fileupload" control (if at all possible) and if it works (or doesn't) then that should tell you something about your issues there. Also, as another test, try to remove all styling from the control you are using, because setting custom styling seemed to really muck-up some of the file upload controls that I tried. Well, that is my saga-- may it one day help a fellow traveller. HTH. Thanks. -- Mark Kamoski