I get http error when I upload large files on my multisite

My media upload quota is 64mb. When I upload files below 10mb I have no problem. However when I upload files larger than 10mb, but smaller the 64mb I get an error message when crunching. I upload my file via FTP using my network successfully, (I thought my network was the issue) but can't upload successfully using the media uploader. I contact my host but they said the problem is not on their side. I need help to fix this.