After further research, I have found out that I have downloaded the 7.2.1 version of the DNN platform. A new release has been released in 3.19.2014, which i think my enviroment has updated automatically. I had no problems with uploading files before. This release made the changes to upload file windows which took it from the regular button to drag and drop.

A little more about the error. It occurs when i have dropped the file to the specific area for upload. I get a javascript error, but the visual for the file comes, the progress bar never moves though. it is frozen like that.

Javascript error is here;

Resources\Shared\components\FileUpload\dnn.FileUpload.js

_processResponse: function (fileName, response) 

if (result.message)

 in the live above result object is null, therefore when trying to get result.message an error occurs. the function is called by

_done: function (e, data) {
            this._processResponse(data.files[0].name, data.result);
   }

Here data object is defined but data.result is null.

data.result(response) is parsed to json and set to result variable above. since data.result(response) is null, json parse comes back as null.

 I have found this much currently, I think this is a general bug rather than something specific to me but i'm not sure. I'll keep posting my findings on the subject as i have found them.

Thanks,

Kaan

I have no entry in my log file. Since it occurs in Javascript, i don't think it is logged, but I have found the cause of the problem and solved it. Here it is;

I have encountered 2 more problems like this while i'm setting up my environment. First one was to uninstall my SQL Server 2008 r2 and install a fresh new copy with LATIN collation, since SQL Scripts was failing in the Turkish collation. Second one was, I was getting a javascript alert when i try to update my site's logo, which says "an error occured". There as you said i've followed the error log and found the problem was again related to Turkish collation.  Under DotNetNuke.Web project (which can be found in the full source code) go to InternalServices -> FileUploadController.cs.  here we have switch(name.ToUpper()) line. This was failing for me since "filter" will be converted to upper as "FİLTER" in Turkish, not "FILTER" and same goes for all the strings which has "i" in them. so i have fixed the problem with name.ToUpper(new CultureInfo("en-US", false));.

After having this current error, i was almost sure that also this has to do something with Turkish collation but as i said before my knowledge was not enough to follow up with the complex code. So today after some research i have found a way to chance system default culture to EN-US which has solved my problem. Now the upload file is working fine.

For the people who are facing the same problem (This is for Windows 7, i'm sure you can find it online for your own operating system);

Go to Control Panel -> Clock, Language and Region  -> Region and Language

Then set the format for your computer to English(United States).

Then go to administrative tab under same window, and copy your settings to  Welcome screen and to new users. 

This seem to solve my problem. You need to find a way to chance your .net environment default culture to EN-US. Hope that helps to others who has the same problem.

Thanks,

Kaan