Okay, so you are saying that in that box the 'don't use signature' option is selected by default? That is weird..
You know what you can do? PM this entire problem to the support account of this board. It will get received by me again, but in the support account I have an option to escalate a PM so that the Yuku people can take a look at it.

You can find the support account here:
http://support.jamesmcavoy.yuku.com/