This seems to only be happening here, so I'm not sure if it's 1.5 or not (if it's the former, I'll be able to see if it happens on KH-Flare now that we've updated), but occasionally when I enter a thread here and click Upload a File, the basic uploader will come up no matter where I click.
There are two things I can think of:
If I leave the thread sitting for a while, it happens
Whatever the issue is happens when I first load the thread and I just don't realize it
That has nothing to do with this as it works most of the time and on other XF forums--if it were disabled, it wouldn't be working at all. This is something else. (Plus, the latest Flash version with the fix is not blocked.)