If after flashing the cure firmware, as you wote the nuvi can display the PC icon when connected with USB cable, most probably it can turn on if you turn it on. It won't freeze. Most probably you can choose only one language (american english) and no voice and no maps also. If that is true try this:
1. If you start the unit and hold your finger in the lower right corner of the screen it will ask you do you want to delete all user data. Tap Yes. This will clear useless information. Be careful it will delete all your favorites.
2. After performing that go to the speedometer page and hold the speedo for 10sec. You would enter in a diagnostic mode. Then touch Developer Info -> Non-volatile -> Clear Non-volatile memory. The nuvi will reboot.
Try this two and then connect nuvi. Also when you connect nuvi with USB cable don't disconnect it immediately. Wait for example 15 minutes. Maybe your computer have show initialization of the memory.