>>If you are using the windows api for ftp, don't install IE11., Stick with IE10
>>
>>After reinstall of IE10 - everything returned to normal
>>
>>http://stackoverflow.com/questions/19683291/wininet-from-ie-11-randomly-returns-error-12003-for-most-ftp-functions
>
>IE 11 also by default doesn't work with SBS 2011 RWA. To make that work you have to add the SBS site as a trusted site, then manually add the URL to the compatibility list.
>
>I wonder whether doing the same thing for the FTP site would make any difference ...

Everyone can make a mistake, but I would expect microsoft to do some testing before they release