Often this can be related to other processes on your system but more often than not, it's because you have other downloads and uploads, such as on a P2P network, that's hogging all your bandwidth. In which case, usually there's not much you can but close the offending application down. Not to however with IE Throttle which allows you to limit the uploads and downloads on your system. You set the limits according to how much bandwidth you have and the program does the rest. You can exclude certain IP addresses however if it's essential that certain programs or pages need lots of bandwidth.
The good thing is that IE Throttle can even be used as a solution over an entire network because you can install it on individual PC's. The problem however is that users can easily uninstall it meaning that they can hog even more bandwidth to their heart's content whilst others suffer. To ensure that lost bandwidth is "caught up with" at a later stage, IE Throttle also features a "bursting mode" which detects when your bandwidth is at low usage and allocates it those applications that have been held back
IE Throttle is a useful little utility that can be of help to those individuals or even organization that have been experiencing bandwidth problems.