Downloads / Images Must Load Completely Before Displaying / Saving?

Whenever I access a file through HTTP, it seems to require that I completely load the file before it will display.

1) For large images, this will result in the whole thing taking some time to load before displaying in its entirety, unlike the usual progressive rendering.

2) For file downloads, this will result in the file being downloaded only after being cached, appearing only when the whole file has finished downloading, unlike the usual process where it can be seen as a progress bar in the browser's download window (for some reason, FTP downloading seems to work normally)

3) For internet streaming video, this means the video will not display until the whole video has been buffered (i.e. will not play until fully loaded)

1) I am on a home network. Other computers (including my old one) do not exhibit similar problems
2) Using Firefox 9.01
3) Win 7 SP1
4) Realtek PCIe GBE controller