Problems centering images on Nokia handsets

Hi,
I'm developing a mobile web site that renders XHTML and uses css to provide styling. When testing my site on Nokia handsets styles that use "text-align : center;" do not center but instead align to the left of the screen.
I know that the stylesheet is being used as all the other attributes appear to work correctly, and the site views fine in Firefox, ie, or on handsets from other manufacturers (Samsung, sony erricson...). The handsets I'm having problems on include: 6280, 6300 and 6500s (it works correctly on an N95)
Does the Nokia browser support this attribute? If not, how do I get images into the centre of the screen?
Any help would be much appreciated!
Cheers
Sab