I just committed some major refactoring to the LWUIT code base the other day, I changed the way Dialogs work so the style of the Dialog UIID actually surrounds the "dialog" as one would expect... This works really well but is highly incompatible since the change required quite a bit of hacks. I also moved the alignment attribute into the Style class which doesn't seem like something that would break compatibility but it does.
If you are running into problems with your existing code try the following:
You can use the old Dialog logic by invoking Dialog.setDialogTitleCompatibilityMode(true);
This is mostly intended as an intermediate solution until you can fix your theme/code.
If you used Dialog style manipulations by changing the Dialog's content pane this will no longer work as expected! You will need to use the Dialog.setDialogStyle/UIID() methods instead.
If you find that alignment is broken for some use cases its usually triggered by changing the style after setting alignment. The solutions for this are to either define the alignment in the theme or just move the alignment setting code to a point after you change the style e.g.:
Will replace the style component in the component and break its alignment, you need to make sure this doesn't happen.