Ayúdenme, no puedo instalar el paquete "MASS".

> library(MASS)
Error in library(MASS) : there is no package called ‘MASS’

Traté de instalar el paquete MASS desde local:

> utils:::menuInstallLocal()  
package ‘MASS’ successfully unpacked and MD5 sums checked  
Warning: cannot remove prior installation of package ‘MASS’

Incluso yo no puedo eliminar "MASA":

> remove.packages("MASS")  
Removing package from ‘C:/Program Files/R/R-3.0.1/library’  
(as ‘lib’ is unspecified)  
Error in find.package(pkgs, lib) : there is no package called ‘MASS’

También con esta opción no pude instalar el paquete:

> options(install.lock=T)  
> utils:::menuInstallLocal()  
package ‘MASS’ successfully unpacked and MD5 sums checked  
Warning: cannot remove prior installation of package ‘MASS’  
Warning: restored ‘MASS’  
Warning message:  
In file.copy(savedcopy, lib, recursive = TRUE) :  
  problem copying C:\Program Files\R\R-3.0.1\library\00LOCK\MASS\libs\x64\MASS.dll to C:\Program Files\R\R-3.0.1\library\MASS\libs\x64\MASS.dll: Permission 

Y con install.packages:

> install.packages("C:\\MASS_7.3-35.zip",repos=NULL)
package ‘MASS’ successfully unpacked and MD5 sums checked  
Warning: cannot remove prior installation of package ‘MASS’  
Warning: restored ‘MASS’  
Warning message:  
In file.copy(savedcopy, lib, recursive = TRUE) :  
  problem copying C:\Program Files\R\R-3.0.1\library\00LOCK\MASS\libs\x64\MASS.dll to C:\Program Files\R\R-3.0.1\library\MASS\libs\x64\MASS.dll: Permission 

Debo mencionar que uso R con ORE (Oracle R Enterprise).