Here's an idea for a test.
- Create a new Hype document.
- Make a new vector shape in that new document.
- Make another new Hype document.
- Copy-and-paste the vector shape into the new document.
That's what I tried... and it worked.
Also, if you look at the thread you mentioned, look at how the latest post ended off...
That sounds like a bug. There might be something screwy going on here... because I'm thinking that it should just work. I imagine when the people at Tumult wake up, they'll probably want to see your Hype document.
Did you try restarting your computer? 
Although, if you're comfortable sending your document to Hype, you might want to use the Help ▸ Report an Issue option. That will let you send the open documents to Hype — along with system information. If you reboot, and then the problem is fixed, the cause of the problem could remain a mystery.