Robert Bialecki wrote:

>In the Captive portal index.php file I added more html (about 150 lines of code) in the redirect
part. (The part that echo html in the allow_portal function)
>
>And here is something wired. Some times after the successful login it only displays half of the
html code. Some times it displays full with out any problems.
>  
>
I have the same experience when m0n0wall redirects to longish URLs.  
Here's my thread with related info. 
http://m0n0.ch/wall/list/?action=show_msg&actionargs[]=105&actionargs[]=32

As a workaround I ended up just stripping HTML from the allow_portal 
function so that the redirect page fits in one packet (doesn't sound 
like this will help in your case though).