You're quite right - my apologies. This is happening because, before the request gets to your plugin, Q2A first checks for a category which matches the path. This is where the error is occurring - in Q2A's own code, not yours. Anyway as you say this bug has been fixed for Q2A 1.5. If you want a workaround for Q2A 1.4.x, check for a # in qa-page-default.php, and if it's there, skip the bit that is commented "Get list of questions...". Sorry again!