Trouble loading package

I am trying to load a package called Rmark, but when I run 

library(Rmark)

I get the following:

library(RMark)

Error in !character.only : invalid argument type
Error in library(RMark) : .First.lib failed for 'RMark'

When I try to load Rmark from the packages menu, I get:

local({pkg <- select.list(sort(.packages(all.available = TRUE)))

+ if(nchar(pkg)) library(pkg, character.only=TRUE)})
Error in !character.only : invalid argument type
Error in library(pkg, character.only = TRUE) : 
  .First.lib failed for 'RMark'

Any ideas what is causing this error?

My OS is Windows XP, and my R version is R.2.10.1

Thanks,
Glenn

*****************************************
Glenn E. Stauffer 
Graduate Research Assistant
Department of Ecology 
Montana State University
Bozeman, MT 59717
406-994-5677
gestauffer at gmail.com