libc6 bug

vim@vim-Aspire-5738:~$ sudo apt-get install libc6=2.15-0ubuntu10.5
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 emacs23 : Depends: libm17n-0 (>= 1.6.1) but it is not going to be installed
           Depends: libsm6 but it is not going to be installed
 libxt6 : Depends: libsm6 but it is not going to be installed
 python-pygame : Depends: libsdl-mixer1.2 but it is not going to be installed
 xpdf : Depends: lesstif2 (>= 1:0.94.4) but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
vim@vim-Aspire-5738:~$