half a loaf

This is strange:
I re-installed win2k/pro last week.
Ever since, when I do a DL, it will stop at EXACTLY 25 or 50% progress.
The message(s) I receive is that the host did a reset on the connection (IE) or that the file couldn't be found on the server (firefox).
I've done this on several (make than many) files, of varying sizes.
I can DL from another machine, running the same SW (earthlink,IE or Firefox).
What is making it stop at exactly the same spot each time?