Thanks adrock for doing the legwork. I guess my content managers don’t upload stuff very often because after months of the system up and running, we just hit it today. But the fix worked. Hope it gets rolled into the next release!
I could be totally wrong.
I have this same problem, and the fix did not work for me. It had no effect whatsoever. I cleared IE cache and tried again just to make sure it wasn’t that.
Might be worth noting that it’s FCKEditor for me, and not TinyMCE, but the issue is the same, which I guess makes sense if it’s an mcpuk issue.