the first thought that comes to mind is that YOUR TRANNY BIT THE BIG ONE
if you are lucky,you can buy some anti-slip conditioners,lucas oil is one of the many manufacturers that make this stuff for backyard mechanics{lol}
try that and if it works SELL,SELL,SELL.
ive also heard cases of too much oil in trans will cause it not to work propperly,but ive only heard,not experienced
if u want to keep it,get it fixed,if not sell it