Comment 141 for bug 531190

I also have this problem. Have stayed with Natty (well, Linux Mint 11) to avoid it, however a recent update has caused it to sleep every time and an added displeasure of wifi failing after waking (anther bug?). Before wifi would fail only sometimes and require reboot now it is all the time. Quick fix was to disable use_time_for_policy in gconf-editor thanks to this bug report.