Thanks to jefexp for the news.
Word is just in that another build of SP2 has managed to slip through Microsoft's hands once again, the previous one being XP SP2 Build 2111.
We can confirm that this build has the tag of 6.00.2900.2126 (xpsp.040503-1841) and it is considered as Pre-RC2. RC2 is most likely to be released in the next fortnight. Screenshots coming soon.
Update: vorte[x] has already patched the uxtheme.dll. See link below.
News source: In-House