USB no longer stays connected
I can give you one suggestion. Based on the what you have posted and based on what I understand do the following thing.

*. Backup all your data through Bluetooth and do a Settings Reset.
(Settings --&gt; Privacy --&gt; Settings reset).

And try to connect to Computer using your USB setup. If still no help do the next step

*. Do a Factory Reset.
(Settings --&gt; Privacy --&gt; Factory data reset).

If still no help then that might be Hardware issue. Go to any Samsung Customer service center. They might replace only the Pins section.