Help with downloading large files in OSX.

I am at the end of my knowledge with an issue that has been occurring for a while. I have a primarily windows environment with a handful of iMacs in the environment. When the users of the Macs try to download large files in Safari, Chrome or Firefox the downloads will begin and then fail with an "unknown network error". This occurs on pretty much any website they try to download files at and the amount that downloads prior to the failures seems to vary anywhere from 30MB to 300MB. Windows systems on the same switches and even Androids and iPhones are able to download through wireless where as the iMacs are not. The network is completely GB. Any help is greatly appreciated.

 

*Edit It appears that the Barracuda Web Filter is seeing the file transfers from HTTPS servers to the [Mac OSx](http://i.imgur.com/NEpAc3T.png) as coming from seemingly random sites The reason the files would vary in how much they could download is because some of the sites the web-filter would see were [allowed and some aren't](http://i.imgur.com/TgBSjnP.png). The Same file being downloaded on a windows computer does not have that random traffic. I believe I am going to put in a ticket with Barracuda. Thanks for the directions to look.