升级到R 3.1.1后运行lmer时出现问题

I'm running Windows XP, and I recently upgraded to R 3.1.1 and updated all the packages. Oddly, I can't run a lmer on my own data any more. My code worked when I was using R 2.15. I also tried using the sleepstudy dataset in the lme4 package, and things worked fine. I'm running Windows XP, and I recently upgraded