yes, there might be caching issue (if you use default settings and cached model metadata provider). I tried to solve these issues with database driven localization provider, but this lib might come too late in your project (understanding that most of the stuff is already done)..
We have a web-site with 12 distinct languages and have implemented localized MVC validation messages using the method described here. Mos of the time it works fine, but occasionally users viewing in one language will get error messages in a different language, as if the cached data annotations are bieng corrupted somehow.
Has anyone encountered ths issue before? If so, did you manage to fix it?