Problem referencing querystring using fb:req-choice

Question

Hi all,

I am building a small facebook application. I am using asp.net and currently working with the fb:req-choice control (tied along with fb:request-form and fb:multi-friend-selector).

Problem is, that when I specify the redirect url for when the user clicks my invitation, instead of getting what I specified: http://apps.facebook.com/myApp/forum.aspx?tId=1&ref=app&code=2.74rRNejG7tpAOqgDCNf8qA__.3600.1275202400-106570384737670%7CPi8JpoHDW3xGuq2lxdZl1d4CLUU.

This is what I am getting:

http://apps.facebook.com/myApp/forum.aspx?tId&code=2.74rRNejG7tpAOqgDCNf8qA__.3600.1275202400-106570384737670%7CPi8JpoHDW3xGuq2lxdZl1d4CLUU.

as you can see my query string isn't getting parsed. Instead, only the first parameter is written, why is that? How can I get this right?