I had the same problem too. However I don't know the cause of it (it seems to happen randomly or so), I know a workaround. I guess check in PHP if the form is submitted by saying
if ($submit) {
...
}
else {
// Show form
}
The $submit var (or however you named your submit-button) is empty, while all other variables are set. So I'd use this
if ($name && $email && $password) {
...
}
else {
// Show form
}
Hope this helps. Greetz,
Vincent Driessen
Venlo, The Netherlands