Unable to check for and update new parts

Open a shell using the SAME user you are running the IDE with and try to do a cd /usr/share/fritzing/fritzing-parts
If you get a permission denied error, check the permissions of each directory, sometimes there is a 'x' permission missing (x is execute permission for files, but it's search permission for directories).

So
cd /usr (should work in any case)
cd share
cd fritzing
cd fritzing-parts

I any of those fails you'll have to add search permissions for your user, do that with "sudo chmod o+x [dir_name]"