Vista's SP also has the compatibility problem.
Far be it from me to speculate on which problem gets fixed first -- auto-updates and downloads have been disabled for each, awaiting release of filters that prevent the SP from being downloaded to systems running RMS.
What the heck. It's no stretch to figure Vista will have the glitch filtered and resume auto-updating before XP. XP users are, after all, more accustomed to waiting. And waiting. And... you know (especially if you're running XP.)
Since is the last XP Service Pack update, it's probably to Microsoft's credit (or something) that they're going to fix the incompatibility issue before releasing the SP to the Web.
But it's also one more in the death-by-a-thousand cuts dance that XP users and XP's manufacturer have been dancing for a long, long time now.