I'm not sure what's causing the IE-specific slowness you are seeing. FWIW, I just uploaded a 575MB file over my LAN from both IE and Mozilla Firefox. It took about 10min in both cases. That was uploading to NeatUpload running on Mono/XSP 184.108.40.206 on Linux. I don't have an IIS/.NET installation where I can upload such large files, so I can't really test it there.
Does the problem still occur if you remove the UploadHttpModule from your web.config? If it does that it isn't associated with NeatUpload. It's either IIS/.NET or your particular IE installation. I'm guessing the latter. Does the problem occur if you try to upload from other computers using IE?
PS. Are you the same user who posted about slow uploads with IE in this other thread?
unfortunately i've the same problem. I've tested version 1.1.1 as well but i's still the same. I've tested it on my companies LAN and saw that on "some" machine upload works really slow with ie. The funny thing is, it works perfectly on the same machines when you try with mozilla or opera. And, on the other hand, it works fine with ie on other machines.
I'm quite puzzled. What else i can try? Do you have any idea?