Nokia :: E72 Freezing - Clock Icon Disappears

I started using an E72 recently and installed the latest software. However there is an annoying problem with it, from time to time, i.e. once a day, it freezes. The phone won´t respond to any key (you can press and nothing happens), except the email key if keep it press it will display the screen to send an email, but that is all.

I found that the problem in clock related. The clock icon disappears from the main screen and anything after will led to a frozen phone, reboot is the only option. Sometimes going to the clock applications solves the problem but not always.

I disable the automatic sync of the clock and left it manual. But that only has halved the occurrence of the problem.