I had exactly the same error. It occurs because qbi_config calls qbi qbi_version which can call qbi_config(if config isn't done yet) and so on in an infinite loop.
A quick hack is to comment out
require(DIR_WS_INCLUDES . 'qbi_version.php');
around line 47 of qbi_config for the first run and complete configuration then just put it back in for normal use.
It seems to be working for me