I had that happen when 5.5.1 first came out. I had to right click and Save As... to get it to download...
...
...although they had the wrong file setup in the file manager. Somehow it sent me UBB French (ubb6104-fr-release-full) instead of UBBThreads. They have since fixed it, and I've download 5.5.1 and installed it, but it was still a bit weird.
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