I can't exactely tell you what's going wrong but i'm currently testing some modication/replace in gta sa ifp ( on the walk_player inter alia )
and i notice that unused bones ( no frame key ) bug in game after export and re-import with 3Dmax .
For an example if i export the original player_walk , without any modification , and re-import and replace the same anim , it makes the jaw of cj bug in game (not in 3Dmax).
I don't know how anims for mouth and other special bone (like breast , jaw , eyebrown , belly ) works in gta.exe but i tentatively fix it by adding keys for all unused bones bugingame .
It seem to work but i didn't properly test it , depend on the rigging of the model.dff .
Anyway , just to say that your mouth problem is not necessarily a problem of conversion between VC and SA .
An other thing is walking and run anims function , with all 4 or 3 speed .
I'm not sure , but the different walk and run speed seem to be mixed together to get a smooth transition .
For an example , when you walk , first there is walk_start , after walk_player , a mix beetween walk_player and run_player , run_player , then run_player and sprint_civi quickly mix and finally sprint_civi .
All that to say if yours foot step of you new animation aren't basiclly the same ( like left foot first .. ) of the anim comming next , it will probably messing around due to the transition .
( i remember 2 years ago testing anim of the walk_player in gta VC and i've got a lots of problems with step order and thing like this ( damn walk start ) )
|I press the button that says set keys. I uncheck the one that says position.|
hummm ... i 'm not sure to understand why did you do this .
One more thing , check if bones of VC and SA are the same , animation in gtavc seem to be very different of sa .
And try with a model of Tommy Vercetti rig for sa because he has a very peculiar walkstyle .
sorry for my english and 'hope you understand but like i was saying , i'm just on it and don't know if all i say is true , it's just my personal conclusions .
 oups , don't see ceedj previous post . Anyway , its didn't discredit my advices . This post has been edited by fishfinger on Friday, Jun 17 2011, 01:35