You shouldn't have had to deactivate your firewall -- unless it was stripping out form parameters.
The IP is an issue, but the current DMOZ scripts are handling it better (you get the message that your submittal was placed in a queue, which means that it will be processed, with a slight delay.) There is, however, something squirrelly going on with Infernal Exploder users. Nobody seems to have a handle on it. Giving ODP's standards-compliance track record, and Microsoft's near-perfect standards-noncompliance record, I'm betting it's some esotoric design defect in the IE.
If you're a particularly public-spirited sort, you could try putting your firewall and proxy server back, downloading Netscape (4.x or 6.x, doesn't matter) and letting us know what happened.