/dev/cgroup messages on launch of bash

I get the following messages when launching bash:

bash: /dev/cgroup/cpu/user/4249/tasks: No such file or directory
bash: /dev/cgroup/cpu/user/4249/notify_on_release: No such file or directory

Don't have a /dev/cgroup at all.
proc 4249 is bash.
I have a phenom II x6 processor - whether that makes a difference I don't know

Not sure what else to say.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: bash 4.2-0ubuntu3
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Sat Jul 16 14:25:58 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
 LANGUAGE=en_GB:en
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: bash
UpgradeStatus: No upgrade log present (probably fresh install)