Thanks for this. This was a bug introduced when trying to fix a different bug, relating to the highlighting of custom links to Q2A pages.
For now you can fix it by replacing the following in qa-page.php:
(strtolower(@$navlink['url'])==$selfpathhtml)
... with ...
false
I'll roll this into Q2A 1.5.1, along with a different way of ensuring custom links to Q2A pages are highlighted correctly.