jQueryUI Accordion overlaps menu on the left hand side

jQueryUI Accordion overlaps menu on the left hand side

Hi,
 
I have been struggling for a couple of hours with a jQuery UI accordion.
For some reason the header of the accordion overlaps the navigation on the left hand side of the screen.
 
The content of the panes is placed correctly, but the header is far too much on the left hand side.
Is there a way to force the position of the headers (an the image)?
 
I'm a newbie with this technology and may ask a stupid question. Please forgive me in advance if it is the case.
 
Is there anything else I should specifiy? The CSS used? the HTML markup?
 
Thanks in advance,
 
Jaepetto