I finally found out how to fix it.

you can remove the "acpi=off" in /etc/default/grub and run update-grub, and reboot

you got it!!

I am seeing the same thing with Indigo, Ubuntu 14.04, Gazebo 2.2 in a Hyper-V hosted virtual machine. acpi is not off in the grub config. I think it is to do with the Linux kernel not picking up the virtualised hardware as a high resolution clock.

Kernel patch found here would probably resolve it for those keen enough to re-roll the kernel; http://permalink.gmane.org/gmane.linux.drivers.driver-project.devel/71390

Another solution would be to grab the gazebo-2.2 code, downgrade the warning to a log or debug message like it probably should be and re-compile. There is a comment above the offending warning in the source that says;

/// \TODO Make this a gzlog
gzwarn << "Sleep time is larger than clock resolution, skipping sleep\n";

So its probably a good call. Recompiling gazebo takes a while though.

Another possible solution is to slow down gazebo's update rate so that the sleep call that generates this warning is longer than the reported cpu's clock resolution. Though I tried this without success.