a var_dump of the post array, the form data being sent, shows that the POST array is being truncated.
This can happen for a couple of reasons.
by default, php will only allow the post array to contain 1000 elements, it looks like your form is exceeding that number.
another possibility is the post_max_size, I Dont think this is it, as the default is 8M, but it should be checked.
You will need to contact the host to have these settings adjusted in the php.ini file.