post your signup.php and takesignup pages in code tags so we can take a look
im 99.9% certain its the main insert query. either the premodded source inserts an IP on signup but the var holding the IP is not being populated or possibly a field mismatch error somewhere
also a little tip ... any sql queries in a script that is not working should be appended with sqlerr(__FILE__,__LINE__); to give you a detailed output of the problem
i.e
Code:
$res = mysql_query("SELECT values FROM table WHERE value='var'");
becomes
Code:
$res = mysql_query("SELECT values FROM table WHERE value='var'") or sqlerr(__FILE__,__LINE__);