[R] Updating packages in Ubuntu feisty for 2.5

[Colleen Doherty]

Hi,
I would like to run R2.5.1 in Ubuntu feisty on an AMD64 chip.
I am a total newbie to Linux.
I have successfully compiled 2.5 however, I am not able to figure out
how to upgrade the packages.
I am not able to find an R-base-core_2.5.1-1_amd64 or all on the CRAN mirrors.
I can find one on the Ubuntu feisty site, however when I try to
install it I get a warning that Dependency is not stisfiable: libc6
I am pretty convinced I have libc6 installed.
When I reinstall it with apt-get It says the latest version is
currently installed.
I would appreciate any help or advice that y'all have.
If this is more appropriate on another list, please let me know where
and I will post it there.
Thanks!

-- 
Colleen Doherty
Thomashow Lab
310 Plant Biology
Michigan State University
East Lansing, MI 48824