have you read how to detect when it needs ivtc, i've written about it at nausia:
http://forum.dead-donkey.com/viewtopic.php?t=7124
If there's ghosting in the source then its unfixable, if you have ghosting otherwise its an indication you've used the wrong method, if its choppy then either the wrong method or it doesn't need ivtc.
Its all in the manual viewing of interlaced and progressive sequences.