that's pretty wierd to have it happen that suddenly. if it was driving fine all day and then suddenly started to shift crappy, it is probably not within the transmission. it could be something with the shift linkage or possibly a broken bushing/bearing somewhere on the tranny or clutch assembly. it doesnt seem to be gear or synchro related though, since those type of problems usually dont happen that suddenly and they usually dotn affect every gear.
OR i can just give the normal generic "tranny problem" diagnosis and say "i think it's the synchro's"
