Kicking out of gear at stops?

My other car just started kicking out of gear just after an abrupt stop if you try to move to soon it just revvs and bangs into gear.
Also seems to do it now on hard cornering..:(
Any ideas??
(winter car..'91 Regal FWD-OD)

Oh, fluid level is good, even tried some LUCAS additive, no improvement..:(

^^^^^^

it actually pops out of gear or is the tranny slipping?

go onto clubgp.com and ask em, they have alot more knowledge than i or anyone in here would on the regal/grand prix