I'd recently had a read of the Granny Buttons Blog by Andrew Denny where he's standing on the bad side of Nokia Maps with a slight problem from the GPS.. hmm..mind you it doesn't seem slight the way he's worded it!
ANyways it seems his n95 took him on a ride around the city. He says that it cussedly avoided the straight route, and in one case (No.2) it actually wanting him to drive away from the direction he wanted, cross a t-junction instead of turning left, and then going right round the neighbourhood and returning to exactly the place he set off! :D .., before going on his way again.
Andrew it's just your phone's way of showing you that it's bored sitting around the house all day doing nothing..must've been bored the poor chap! I'm planning to take mine on a trip on one of those one way highways soon, I'm sure he won't let me down. Pray for me!
P.S: If you update your phone with the new firmware I'm sure it will set things right.