When I try to load the 'car' package I get this error:
library(car)
Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]) : 
  namespace 'nlme' 3.1-122 is already loaded, but >= 3.1.123 is required
Error: package or namespace load failed for 'car'
But when I run update.packages() there is nothing to update. I'm using MRO 3.2.3 if that matters.
                        
I had the same problem and solved it simply by installing
nlme_3.1-123.tar.gzfrom https://cran.r-project.org/src/contrib/Archive/nlme/