problem with dir() in R-2.1.0?

Hi,

I always use dir(pattern="*.RData") in all the earlier version of R (1.8, 1.9, 2.0.1).

Error messege is as below:
Error in list.files(path, pattern, all.files, full.names, recursive) :
        invalid 'pattern' regular expression

Does anyone have an idea what's going on? How should I define the pattern I need in R-2.1.0?

Thanks!


Bin