If you are using the 3FC ticker, are you selecting the right code to copy and past into your signature?
It is the first one presented and looks like this:
*url=http://www.3fatchicks.com/] *img]http://www.3fatchicks.net/img/heartbar/slider-hearts/lb/204/175/199/.png[/img] [/url] with a [ replacing my *.
Give it a try.
Suzanne also posted detailed instructions in this thread.
http://www.3fatchicks.com/forum/showthread.php?t=56332
I'll be online for a bit longer and will watch for your siggy.