Yesterday I removed R2.11 from my system (Win7, 64bit), since I´m working on R2.13.
Since then i get an error message:
> require(rJava) Lade nötig
I solved it by following these steps
Sys.setenv(JAVA_HOME='C:\\Program Files (x86)\\Java\\jre6')
install.packages('rJava', .libPaths()[1], 'http://www.rforge.net/')