I tried it on 3.4.2 and the problem was that you filled out the form, and hit login, but it didn't log you in for some reason.
Now I'm not a programmer, but I did really well on pattern detection in an IQ test, so I think I have a fix

It seems to work fine, the problem was with the following call to header function:
Code:
header("Location: ../$redirect/cart.php");
In my version, the original login.php used the format:
Code:
func_header_location("../$redirect/cart.php");
There are two instances in the mod snippet that require changing, but that's all and it seems to work like a charm
So in the 3.4.2 version, the mod will be as follows:
Original File: login.php (line 125)
Code:
if ($login_type=="C") {
if(!func_is_cart_empty($cart))
func_header_location("../$redirect/cart.php");
else
func_header_location("../$redirect/home.php");
}
Modified File: login.php
Code:
if ($login_type=="C") {
if(!func_is_cart_empty($cart))
func_header_location("../$redirect/cart.php");
else {
$relo_page = strrchr($_SERVER['HTTP_REFERER'], '/');
$relo_page = str_replace('/', '', $relo_page);
func_header_location("../$redirect/$relo_page");
}
HTH, lemme know if it works for you.
P.S. This works even if the customer is registering during checkout, and redirects them back to the page they were on, so they don't have to hit 'checkout' again

I loved that!