This bug has been around for a while now. Unfortunately, there does not appear to be a fix once it has occured. Always save your game before travelling, it is rare, but not impossible, for it to happen twice in a row. Go back to your last save and try again is the only solution I know of. If it happens a second time, it may be best to exit the game completely and reload before trying a third time.
I have had one game where I simply could not travel (I had 3 attempts), but, as it was at the very start of the game, I simply restarted the sims and started a new game.