I've found a bug in which, upon editing a replay on the first frame under certain conditions, it messes with how your character is positioned.

I am running Toribash 4.31 on Mac OS X Lion Version 10.7.5 through Steam, though I've found the bug still occurs whether it's through Steam or not.

In order to get this bug to work, this is what you do (images are large, and are thus not embedded):

First, move the tori in any way:
http://i.imgur.com/SgoVMwj.jpg

Space a few frames; not really important how many, as it works regardless of how many. The bug only occurs if you don't move any body parts after the initial frame:
http://i.imgur.com/6FS5ZrI.jpg

Go to edit this replay and pause it on the very first frame, as shown:
http://i.imgur.com/LfPKdyk.jpg

Upon pressing e to edit, your tori should snap to whatever position you stopped on in step 2. Everything will be relaxed, including uke, and all grabs will be reset:
http://i.imgur.com/yOL1y6J.jpg

This allows you to make replays not starting from the default T-shape, as attached.

Replay editing is broken in 4.31. IMO don't bother with single player of any replay editing unless you're using an older version.

Any version in particular that you recommend?

3.9 worked well for it. So did 4.1 iirc.

4.2 works just fine.

Where can we download past versions of TB?
Is it on the site?

From Jarmund's: http://toribash.jarmund.net/clients/