I got a very similiar problem.
With my Telekom sim it seems to hung at the dots but it just takes 10minutes to boot, with another o2 sim or no sim it doesnt take so much time there.
But after booting every seems to take very long time to start, but there is no high load or excessive memory usage!
If i boot in Offlinemode and then go online, it works with both sim!
Just everything take long long time to start and react and somtimes crash.
also the keyboard backlight flickers if the display goes off. thats very odd.