I have a Samsung Captivate on ATT. When connecting USB Cable > Mass Storage > Connect storage to PC the app crashes once .. then if i try again really gets mad at me and shuts down my phone.

After hours of trying various things and searching online forums, I contacted Samsung chat support. They suggested a soft reset (pulling out the battery for 30 seconds). This did not help me.

Then after asking a few questions about my USB Cable, he asked I try another USB port. Bingo! It worked. 

It could be an issue with my USB port or with the cable itself, the tech said.

I hope if you had the same problem or a similar problem this was able to help you.  If it was, feel free to leave a comment.  I’m always curious.