Tried your link through both IE and AOL. Same results- form field appears for split second- then gone. I have tried hovering my cursor over the area where the form field is (when the page first loads) and what I can see is that it's the tabs for navigating other areas of your site (only the black tabs appear, the rest isn't there).
I ran a full scan of everything yesterday, after installing the Home Version. Had 19 detections of Win32:Trojan-gen{other} turn up and selected to delete. Scan reported that they were deleted. Avast is on and scanning, no alerts. I've had no problems other than trying to access the registration page on your site.