tinymce: style for IMG tag

I've installed the tinymce module so that my less experienced users can 
more easily edit their own pages.  Everything is going fine, except that 
I don't seem to be able to apply a style to an image.

I've got a css style defined as:

".left { float:left; margin:10px; margin-left:0px;}"

which I usually apply to either DIV or IMG elements.

The style "left" does show up in the list of available styles when 
editing using tinymce, and I can successfuly apply it to DIV or P tags, 
but not to images!

I should say _new_ images in a page, as existing images that I've 
inserted into a page (using normal html editing) can be of classified as 
"left", and Tinymce says down at the bottom of the editor that they're 
"img.left".

But I can't apply this style to an image by selecting the image and then 
selecting "left" from the dropdown list of styles.

NOTE: other styles that I've defined have the same problem... I can't 
apply them to images.

I have the "advimage" plug-in loaded, and it works well.  I've followed 
the advimage instructions and added 
"img[class|style|src|border=0|alt|title|hspace|vspace|width|height|align|onmouseover|onmouseout]" 
to the list of additional tags.

Versions:
xaraya 1.1.2
tinymce 1.1.1

Thanks, Steve.