Arkose: It's easy enough to set up the server such that it allows resuming but only permits a certain number of simultaneous connections per IP, so the core benefits of a download manager still work while the burden on the server is identical to downloading through the browser as usual.
DukeNukemForever: You should try to allow in JDownloader only one connection to the server, maybe that helps. If not, give DownThemAll or Free Download Manager a try.
Hmm i never considered that JDownload may default in sending out several connections at once to pull with. I'll have to look over it's setup opitons and see if I can lower them to one.
carnival73: Everyone knows that downloading over 2 gigs through Firefox is near impossible without a mishap taking place and the download getting stopped.
Dzsono: Yeah, Firefox isn't good for that. Although, that is changing slowly. Chrome is better for large files and the competition is forcing Firefox to catch up. I haven't tried because I use JDownloader, but my 64-bit build (Cyberfox) might also be a better option for large files. I'd consider moving to it anyway; it's super fast.
I used Chrome previously but was never able to figure which were it's cache or cookies folders. I found the main one but suspected there were a few more pulling and storing marketing tracers. I don't trust ASC or CClearner alone. With Fox I usually go in and delete the entire (oddly named) folder under Profiles In Mozilla's Local folder.