You gesture at a ship's rat.
A lance of silvery-blue light forms between your hands. Turning slightly, you throw the lance at a ship's rat!
Your stance makes it difficult to manipulate the mana streams, causing the spell pattern to collapse at the last moment.

Whenever I try to cast a targeted spell I keep getting this message, what am I doing wrong?

The situation is I'm in combat, fighting rats usually more then one, and here are the commands I use:

prep aet lance (wait for it to fully prep)
target rat (wait for it to fully target)
cast and I always get the above message which I copied directly from the game. What Stance are they talking about?

Any suggestions, hints or criticism will be greatly appreciated.

Your attack stance is below 100 so you aren't putting your full force into your attack. Set your STANCE ATTACK 100 and that should fix your problems.