After reloading a world (quitting, then opening it, or any other world) wire connectivity will change. For example, a red wire next to a switch will by default connect to the switch and be powered by it, but after reloading the world the only way for the switch to power it is by being inside the same block (Multipart). It seems to be some issue of most wires just refusing to connect to anything but wires after reloading a world. Restarting minecraft completely will cause it to revert back to default behavior, but only until you quit the world and load it up again.

Was reported before, but i couldn't reproduce until now. Will fix...

Fixed via 076bb50