LHC@home

I haven't used boinc in a while, but I have installed the latest version today. When I use the GUI to attach to a project. It says that there is internet problems and should try to restart it. When I attach with the terminal it does it successfully, but when I start up the GUI it says it cannot connect; password is incorrect. How do I overcome this?

Since you can connect to any core-client running on any machine reachable (even over the internet), each client starting with 4.2x (or so) should have a password set to restrict manager access.
Since 5.x.x this password-file "gui_rpc_auth.cfg" located in the main directory where boinc is installed is part of the distribution and set to an default value.
So nobody can connect to this client if the user of it doesn't care about it. The previous ones came without this file, so everybody could connect and control this core-client without authentication.

Look for this file and enter your own password using your favourite editor. The password is the only content of this file.

Then restart the core-client and fire up the GUI afterwards. It will ask for your password as always but now you know it ;-)