R2.0.1 for Mac OS X 10.3 problem

     I have the same problem, in Windows, and I think
the .Rdata is not corrupted. Load R without loading
the.Rdata file - move or rename it. Then library(lme4)
and load the .Rdata - it should work.

This also is my experience (in Linux & MacOS X). The .RData need not be
corrupted, but you have "corrupted" your R installation by deleting or
corrupting some package using S4 methods (like failed upgrade of a S4
method package). When you start R so that it tries to restore those S4
objects in .RData, you get the error. Renaming or deleting .RData will
help, of course. Alternatively, in my case it helped to start R with
option --no-restore-data (in Mac when starting R from terminal -- where
you are all the time in Linux). Probably it would help to install again
the original S4 package. (In my case this happened when I tried Thomas
Yee's VGAM and then removed the package.)

cheers, jari oksanen

Jari Oksanen -- Dept Biology, Univ Oulu, 90014 Oulu, Finland
email jari.oksanen at oulu.fi, homepage http://cc.oulu.fi/~jarioksa/