Do you have xz-utils installed (if it's tar problem)?
Is this for Ubuntu 10.04 or 12.04? Your first line says 10.04 but your err msg mentions something more recent.
EDIT: and yes, I agree with Majk578. Check for xz-utils.
We're adding a dependency on xz-utils for the next package update. Thanks!
Nothing extracted yet.
Running Ubuntu 10.04, after I download and run the installer, I get the following error:
user@ubuntu:~$ steam
Setting up Steam content in /home/user/.local/share/Steam
tar: xz: Cannot exec: No such file or directory
tar: Error is not recoverable: exiting now
tar: Child returned status 2
tar: Exiting with failure status due to previous errors
Failed to extract /usr/lib/steam/bootstraplinux_ubuntu12_32.tar.xz, aborting installation.
The tar it mentions exists, but apparently can't be extracted? I tried reinstalling and it keeps happening.