thank you for reporting this problem to us!
Currently we are aware of the upload/download problem and still investigating the problem.
It looks like that not all users are affected by this problem but at least for downloads you might use download managers
like http://www.downthemall.net/ for Firefox and aria2c for the command line as a workaround.
I understand that this problem has an impact to your business and you are worried about your customer relationship.
So do we. To constantly improve Studio we need your input. So you might take some time for sending me some information about your OS (if Linux, which distro/kernel version) from where you are not able to upload files from.