I'm using Win7 with IE 11.0.3. I also began having this problem about 1-2 weeks ago. I have double checked file sizes prior to uploading them to be certain they are within the allowable file size requirements. Today, the only way I could upload was to change my settings to the standard editor and use the basic uploader to upload one file at a time. Finally worked, but I used to be able to upload multiple files with the advanced WYSIWYG editor. When trying that method now, I don't get the option to upload multiple files, and the basic uploader lets me select a file, but then simply hangs when I press the upload button.