Comment 7 for bug 662853

Confirmed, I suffer the same issue:

System becomes unresponsive.

When running 'top', the process 'polkitd' is listed at top, taking anything from 40%-90% memory (I have 4GB installed)
When the process it killed via 'sudo kill {pid}' the system becomes responsive again.

I am running Ubuntu on a laptop, which I suspend overnight, not sure if this is any way related.

$ uname -r
2.6.35-23-generic-pae

cat /etc/issue
Ubuntu 10.10 \n \l