There are some serious device connection issues with BaseCamp 4.1.0. That is why we pulled it from the auto-update servers. You can still download it from http://www8.garmin.com/support/download_details.jsp?id=4435 if you want to.
We are working on fixing the most pressing issues. They will be addressed in BaseCamp 4.1.1.
I'll outline the 2 most common issues and how to work around them in case you already installed 4.1.0:
1. You have a device connected and start BaseCamp, or you have BaseCamp running and connect a device -> BaseCamp stops responding.
Fix: This is most likely caused by a gpi file on your GPS. Look for 006D135900.gpi in the .System or POI folder. Rename the file to something else (006D135900.bak for example). Restart BaseCamp.
2. BaseCamp 4.1 does not recognize your Nuvi, but earlier versions of BaseCamp did.
Fix: Switching the device to Mass Storage mode might fix this. Disconnect the device. Turn it on. Go to the Odometer screen (View Map, tap speed). Press your finger on the odometer for around 10 seconds. A debug screen should appear. Go to MTP settings. Select Mass Storage mode. Connect the device to BaseCamp.
I apologize for all the trouble. This is something we should have caught before releasing, but it slipped through somehow.