Error in installation a R package

There could be a few things happening here. Start by first figuring out your library location:

Sys.getenv("R_LIBS_USER")

or

.libPaths()

We already know yours from the info you gave: C:\Program Files\R\R-3.0.1\library

I believe you have a file in there called: 00LOCK. From ?install.packages:

Note that it is possible for the package installation to fail so badly that the lock directory is not removed: this inhibits any further installs to the library directory (or for --pkglock, of the package) until the lock directory is removed manually.

You need to delete that file. If you had the pacman package installed you could have simply used p_unlock() and the 00LOCK file is removed. You can't install pacman now until the 00LOCK file is removed.

To install pacman use:

install.packages("pacman")

There may be a second issue. This is where you somehow corrupted MASS. This can occur, in my experience, if you try to update a package while it is in use in another R session. I'm sure there's other ways to cause this as well. To solve this problem try:

1. Close out of all R sessions (use task manager to ensure you're truly R session free) Ctrl + Alt + Delete
2. Go to your library location Sys.getenv("R_LIBS_USER"). In your case this is: C:\Program Files\R\R-3.0.1\library
3. Manually delete the MASS package
4. Fire up a vanilla session of R
5. Install MASS via install.packages("MASS")

If any of this works please let me know what worked.

I had the same problem with e1071 package. Just close any other R sessions running parallelly and you will be good to go.