Possible Duplicate:
The message about a new answer being posted should refresh the page
I was answering this meta question, as I saw two new answer notification pop up in quick succession. When I clicked them to see the answers, I noticed they were both the same answer (same Post ID, as it could be seen from their edit links). Here is a screenshot:
After refreshing the page, the duplicate was gone. Looks like a minor UI bug - but still a bug.