Nokia Nseries :: N8 CPU Usage Goes To 100% Whenever Keylock Activated?

As the heading states we have an N8 in the office (one of about 5) which exhibits a very strange symptom. After the first few days of having terrible battery life, even when doing very little with the phone, we tracked down the error to something which happens when keylock gets activated the first time after starting the phone. Using Nokia Energy profiler, we've found out that as soon as keylock is activated the CPU usage goes to 100% and never comes down afterwards, except when turning phone off and on again. Done factory resets (via phone meny, Restore and Delete data) and this problem shows up even when installing only the most basic apps - last time it appeared after installing swype, so now resetting and installing nothing.