auto gearbox..

[nick]

hi everyone, i got a prob with my gearbox not changing from drive to 3rd and from 3rd to drive, it works down and up from 3rd, now does anyone know what the prob might be, i,m thinking it might be one of the auto clutches, or there might just be some crap in the gearbox causing it to stick, sometimes its ok then my transmission light comes on, the car goes into crawl, i have to switch of the engine for a minute, then it sorts itself out for a while, recon box i,ve been told is £1200, don,t fancy paying that if it can be sorted, any advise would be great..cheers