After installing the daily update on my Lenovo T61 and rebooting the system, I had some strange issues with the kernel processes kworker and watchdog. Either kworker or watchdog took about 60% of the CPU power. Unfortunately switching back to an older kernel version did not fix it. Thus after searching the web, I found out that this problem is related to the network connection (see  for details). Since I am using wifi to connect, I disabled my ethernet interface by
ifconfig eth0 down
, which solved the problem.
I know this is not a general solution to this problem, but it may help wifi-only users as I am.