[WoW] Slave not assisting but works other way around

Hi, I have a very strange problem...

My slave toon which I have resized on my second monitor does not target (assist) my target whenever pressing the hotkeys (1-9) yet it will broadcast the key press if it has a target.
Yet if I switch them round, i.e. my main is acting as slave then it will assist me.

Some may say well use them the other way around but I don't want this because I have my main account which I use for non-boxing which has a lot of bound on account stuff and if I am boxing then it becomes akward when in the situation where I do need to use the other character and it doesn't assist.

I've used the quick setup wizard and it's exactly the same as my successful dual-shaman character setup which is flawless.

Anybody got any ideas?

Config: http://www.privatepaste.com/4fc07b20b8

[lax]

1. Make sure the ISBoxer Addon is enabled in the window that won't assist
2. Go into the in-game key bindings in the window that won't assist, set an empty key binding to Shift+Backspace, and then unbind it again -- FAQ: I recently set a key binding in the game and now assist doesn't work?

2. Go into the in-game key bindings in the window that won't assist, set an empty key binding to Shift+Backspace, and then unbind it again -- FAQ: I recently set a key binding in the game and now assist doesn't work?

Someone on Dual-boxing.com beat you to it but this did fix it although nothing was bound to the required key