^^&*^ network cable

every time i try and upload something, be it to imageshack, broadcube, or anywhere else (although imageshack and broadcube are by far the most common), i get one of those stupid pop-up bubbles telling me a network cable is unplugged. the internet promptly dies, and i have to start the upload again. lo and behold, it crashes again. repeat cycle for several weeks.

this happens anywhere between 2 and ten minutes after i commence the upload. it happens on every upload, and only while uploading. any suggestions as to what might be wrong here?