Engine stalls and speedometer fails

I have an Opel Corsa/Holden Barina 1998 that has done 150000 kms which has started to stall after drives of approx 45min. The car will run fine on the highway, it is only once you need to change down gears and slow down that the engine stalls. At the same time the check engine light comes on and the speedometer starts going all over the place, until eventually it stops working all togther. Car starts perfectly again, no problem. What could this be? Any help would be appreciated.[/B][/i]