Having Login in the workflow breaks checkout

Hi,

The white page indicates that there is a PHP error, so you have to activate the debug mode.
Without any real error information we can't help you.

Regards,

It doesn't mean that the checkout takes 24M. It just means that all the extensions installed and loaded plus joomla plus the processing that is done during the login adds up to 24M.
During the checkout, a lot of things have to be done/checkout and it can add up to a few M.

24M is actually pretty low for a joomla website with a few extensions on it. Heck, just creating a thumbnail of one big image would easily go above that memory limit as the GD library, which is used in PHP for images processing, has to load the full image in memory and eats up a lot more than the size of the compressed image (approx the same as a bmp of the image).

As per the PHP manual ( php.net/manual/en/ini.core.php ), the default value for the memory_limit is 128M.
But even 64M should be way enough for any type of HikaShop store (including joomla and other extensions).
With a normal store 32M should already be enough. Yours was set to 24M, not 32M as you can see in the error message: Allowed memory size of 25165824 bytes exhausted.