I haven't seen this posted before. I just had a colony ship on one side of the map completed. I launched this ship and set it to colonize Planet Ireland III (class 5) on the other side of the map, took 30+ weeks to get there. When I click the planet to travel to the ship doesn't move and there is no path. When I click near the planet the ship moves and creates a path. I have a saved game and a debug.err file if you want me to send it in. Here are two pictures showing this as best I can. The first one shows the path near the planet.

this second image shows after I clicked the planet.