I had the same problem with you.But it is resoved now.
The solution is:

Don't put too many image files and media files on your card.If you had to zip it to one file.I guess some threads scan the file when you shutdown the unit.

You had to pull off the battery and press the power on button to reset the unit if it won't power on.

If I had 10000+ file on my CD card. 90% it won't boot up
After I cleaned all the file.Less than 5%.

Good luck