CMS Made Simple Forums

I have a problem with selfregistration module.
If user tries to register with Firefox browser everything is ok.
If user tries to register with Internet Explorer empty page will be displayed. There is still one exceptionl. If user fills all the fields then registration is completed.

I would be happy to receive some comments why is that so...
The web page is still on development, so You all can try to register yourself:)
http://www.wwoof.ee/index.php?page=volunteer-2&hl=en

I found out, that maximum length of URL in internet explorer is 2048 chars if get method is used.
I looked from the source code and found out, that actually the form method is "post"

Now i have question that why are all the parameters on address bar, when form post method is "post"?

Any ideas?