apt-get upgrade: no file name for libattr1

Built using the installer - 6-18-12 - I thought I had previously successfully run apt-get update, upgrade and rpi-update. Today when I try to update, upgrade I get 1 not fully installed or removed. Then upgrade halts with E: internal error. No file name for libattr1

Am I starting from scratch again or has someone got any ideas. Libattr1 is the extended attribute shared library so apt-get remove then apt-get install is not an option.

I have found that, at times, files are not available.
They could be in the process of being upgraded or replaced themselves.
I would just leave it for now and try again later.

I think I have sorted it.
I attempted to 'apt-get install --reinstall libattr1', expecting it to fail since I assumed it needed to use libattr1 so 'cd /var/cache/apt/archive' and then 'dpkg -i' the package and bingo - apt-get upgrade working again