I convinced a friend to sign up during the promotion, but he was unable to use the web form.
He tried FireFox for a while, and eventually tried IE but it didn't work either. I sent the link electronically and he confirmed it was not truncated. He sent it back to me and I could click the same link in Chrome and it worked, so it wasn't an issue with a malformed link.
He didn't have time to extensively troubleshoot, and he ended up not creating accounts for himself and his wife as he'd intended to.
At first I wasn't even going to bother reporting it (it happened Jan 2), - it isn't a big deal for us, he's got other games he's happy with and we play real D&D often enough that DDO would be nice but won't be sorely missed. But it's a lost opportunity for you so I figured you should at least know about it.
These days everybody is (rightfully) concerned with security, so it would make sense for you to design at least the signup pages to be free of the threats commonly blocked - flash, redirects, ActiveX, and client side scripts. Honestly, you don't even need cookies or CSS for a signup page. It's not like your signup page has to scale to a million hits per hour, you could easily handle all the scripts and state server side.
If you do change it, or have an explanation of what was happening, I am curious and will check back on this post.
Thanks