I am having the above issue on a local server install, all other media files are able to be uploaded without issue.
Server 2012 R2 + IIS 8
I Have tried the following:
I increased the memory limit and max-upload in PHP.ini
Tried a clean install again of all components with a default theme - in case it was a theme issue - still no good.
BTW I also have the same issue on a windows 2008 server ( same versions of MYSQL and PHP )
Anyone have an ideas as to what this may be?