[R] problem with library()

[R Heberto Ghezzo, Dr]

Hello, I am running Win XP in a notebook IEEE, I have R-2-15.0 and R-2.15.1. In a subdirectory Cran I
have the packages I downloaded from CRAN (all), after last update when I type
> library()
Error in .readRDS(pfile) : unknown input format
>
a very old R-2.4.0 sitting in a corner and not used for a long time with a very reduced Cran subdirectory, OK at the time, library() works OK. So I assume, without any knowledge, that the problem may be that the list of packages has somehow overstep a limit in Win XP, or in the limited RAM of the notebook (1 G total).
Can somebody shed any light?
Thanks

R.Heberto Ghezzo Ph.D.
Montreal - Canada