First up is changing the collision from the ur-retarded point-tile collision to a four corners collision. It's not ideal but should work adequately, and appears to do so for the player.
I'll let you know if the same is true when I change the NPCs to use it. *groan*
I'm also planning on cleaning up the AI code to see if there is possibly some sort of problem with regards to collision there. I'm not looking forward to going back in there, unless I'm going to come out with about 500 fewer lines of code there than I did when I went in.
Finally, I think some of the projectile weapon and damage calculation code is broken in the fighting engine, this will also get cleaned up hopefully.
The end result should be a smaller, faster, and compatible CSRPG2 executable that you should be able to just drop in your existing copy and have fun with.