Just bought a new Flip UltraHD at Costco and I'm already having issues. The FlipShare software wanted to update the camera, but I received repeated errors:

Error code: 27, 2
An error occurred while interacting with your camcorder. Please make sure your camcorder is connected to your computer.
Error removing file '/Volumes/FLIPVIDEO/System/VIEWER/mem_size.txt'.
Thread info: Upgrade camcorder software : {7e00ce54-bccf-41cc-a2ed-2f0342e16b38}

Bah! Google to the rescue! I found that the problem was due to locked files on the device and that you could reset the flags on the files, enabling the software update to work. So I ran the following from the terminal:

find /Volumes/FLIPVIDEO -flags +uchg -print0 | xargs -0 chflags nouchg

I then restarted FlipShare and the software installed just fine. Thanks to TDD for the tip!