I am having similar errors, but only after I switched from "regular view" to "classic view" in Natty 11.04. I did this to try to work around a bug in VNC, detailed here: https://bugs.launchpad.net/ubuntu/+source/vino/+bug/772873
While in classic view, the xsession-error file grew to 45GB in 48 hours. Now that I am back to the regular view, these errors are largely gone.
I am having similar errors, but only after I switched from "regular view" to "classic view" in Natty 11.04. I did this to try to work around a bug in VNC, detailed here: https:/ /bugs.launchpad .net/ubuntu/ +source/ vino/+bug/ 772873
While in classic view, the xsession-error file grew to 45GB in 48 hours. Now that I am back to the regular view, these errors are largely gone.