Hi,
It's not a memory limitation. I think it's more a buffer limitation.
The configuration page stops during the "acl tab".
I have modified the "config config" view in order to no display this tab and the config is not displayed fine.
After that, I have reactivate the ACL tab and I have comment some options in the ACL tab, the page still displayed fine but if I display all elements, the page break.
The strange thing is that, removing just one element in the ACL tab fix the problem.
There is no error or memory reach problem with the ACL display, by removing one element (and having a good config page), the Joomla debug said that just 17MB has been allocated.
So I think that the config page is too big, it contains too much data for your PHP buffer configuration.
Regards,