There have been a few queries recently about using my chemstyle package with XeTeX. The problems arise when people attempt to use the \schemeref macro, which is defined by the ‘low-level’ chemscheme package, which is loaded by chemstyle. For those of you not familiar with the package, it’s for chemistry graphics (which are usually called ‘schemes’), and is for putting in reference numbers automatically.
The problems arise because chemstyle ultimately relies on psfrag for the graphic manipulations. To the best of my knowledge, psfrag can’t be made to work with XeTeX, which means that neither can my \schemeref macro. I’ve just uploaded a version of chemstyle to CTAN which says this, and issues a warning if used with XeTeX. I do hope that helps a little.