If you are using a web application that generates PDF files for you to download and view or print, you may eventually run into this problem. If the web application does not generate a new filename for each PDF, eventually you will have more than 1000 PDF files with the same name and IE will silently stop working.
For example if the generated PDF file is called Download.pdf, the first time you download the file, it will be called Download.pdf. The second time it will be Download(1).pdf . The thousandth time it will be called Download(999).pdf. After that, you will not be able to download the file any more.
The solution is to empty your downloads folder.