getting connection resets with host's ftp

I can't seem to upload large avi files to my webhost's server. The most that I can upload in one shot is 5mb, but then the connection resets and it starts all over again.

I contacted them about this, and they told me to go to my ISP. ISP says they don't restrict uploads.

So now I look at my router.

I used to have many lag spikes with counter-strike until I disabled wireless zero config, and I haven't had any lag spikes since then. But now I wonder if there's something else I need to change that doesn't like my maximum upload bandwidth being used.

Does anyone know what could be causing this?