::::::FileSonic's FAQ says: "If you do not have a FileSonic Premium account, certain restrictions may prevent you from downloading: We do not allow more than one concurrent download per IP address and also limit the amount of data you can download from our servers within a certain timespan. If you share your IP address with other FileSonic users (e.g. because your ISP uses proxies or NAT), you may be adversely affected by their activities." This could clearly lead to issues with an IWF proxy, although any type of proxy could set off this problem. The file hosting sites have these restrictions for free users to prevent excessive use in a short period of time.