Hi,
That error indicates that the memory on the page reached the limit allowed by your server.
There are several ways to solve that and the fact that you have the error on the checkout of HikaShop doesn't necessarily means that it comes from HikaShop.
You can try to increase the memory_limit parameter of your php.ini. Try increasing it to 256M instead of 1228M.
You can try to switch to the default template to see if you still have the problem or not (which would provide information on whether the problem is linked to the template or not). And you can do a similar procedure with the plugins of the groups "system" and "hikashop" by disabling them one by one to see if that helps.
We reply as fast as we can. If you want to get a useful solution faster, it's best to directly provide accurate information when you have a problem. As we ask when you create a new thread, if you can provide the error message and a link to the page that would already be better. Right now we can't look at the problem, and you didn't even provided the full error message which contains sometimes crutial information on the file and line where the problem comes from.