evaluation is nested too deeply: infinite recursion?

I recently started using R (Version 1.3.0 on a Dell machine).  After using
R for about a week, I started receiving the error message shown below.
I can't even run simple commands that I know should work.  

Is this a bug or did I just mess something up? I've uninstalled and
reinstalled R but continue to receive the same errors.   

The errors are shown below:


R : Copyright 2001, The R Development Core Team
Version 1.3.0  (2001-06-22)

 
help(sum)

Error in as.double.default(U) : evaluation is nested too deeply: infinite recursion?

lm(rnorm(100)~rnorm(100))

Error in as.vector(data) : evaluation is nested too deeply: infinite recursion?

Thank you very much for considering my problem.

Jason