About a month ago I had the same thing happen to me on the way to work. Reverse was 1st gear, 1st was 3rd, no reverse at all etc. The bad news was that it was the selector forks inside the gearbox, so I had to get a recon 'box. May not be exactly the same thing but sound similar, but I know of other people that have had this happen and it was just a nut missing off the gear selector mounted on top of the gearbox. I paid £550 for a recon 'box with 2 year/24k warranty!