R help - Jan 2008 - Two warning messages after loading package 'coda'...

Hello!
Recently I updated my R and all packages, under Linux (Ubuntu 6.06). 
After that, I started to receive warning messages:
1: In namespaceImportFrom(self, asNamespace(ns)) :
  replacing previous import: cov2cor
2: In namespaceImportFrom(self, asNamespace(ns)) :
  replacing previous import: xtabs

This is happening when I load 'coda' package, after Hmisc, survival, 
stats, utils, graphics, splines, Design, lattice, zipfR, lme4 and 
Matrix. There are no problems at all, and R is running flawlessly. 
However, I would like to know more about the messages and should I 
worry. Can anyone elaborate on that?

Sincerely,
PM