VirtualBox-4.1.16: causes 100% CPU on the host system

[Yuri]

I observe this on the idle Ubuntu64 guest.

84759 yuri           26  20    0  2814M  2157M uwait   4  52:14 101.46% 
VirtualBox // corresponds to Ubuntu64
  2661 root            1  28    0  1133M 73736K select  3 395:05 13.87% Xorg
10915 yuri            5  20    0   798M 84536K uwait   1  37:55 5.08% kwin
11375 yuri            3  28    0   506M 57560K kqread  6  23:42 4.88% 
kdeinit4
84886 yuri           25  20    0  2709M  2158M select  4  16:34 0.98% 
VirtualBox  // corresponds to Ubuntu32
...

Yuri