Comment 118 for bug 762918

I've got the problem too. Looks like a segfault in gnome-screensaver or libcairo.

1) lsb_release -rd
Description: Ubuntu 11.10
Release: 11.10

2) apt-cache policy gnome-screensaver
Installed: 3.2.0-0ubuntu1
Candidate: 3.2.0-0ubuntu1
Version table:
*** 3.2.0-0ubuntu1 0
  500 http://us.archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages
  100 /var/lib/dpkg/status

3) When the screen is locked, typically it should resume after mouse movement or keyboard input and provide a log-in prompt.
4) When mouse or keyboard event happen after screen lock, the cursor will move around but the screen is blank. I am able to access a non-X terminal via ctrl-alt-F1, but the X server is hung and must be killed.

The output of dmesg | tail is

[16621.910506] [<ffffffff8117939a>] do_vfs_ioctl+0x8a/0x340
[16621.910508] [<ffffffff811796e1>] sys_ioctl+0x91/0xa0
[16621.910512] [<ffffffff815f22c2>] system_call_fastpath+0x16/0x1b
[16621.910514] ---[ end trace ce3b9456974e9ef8 ]---
[16625.532183] usb 2-5.3.4: USB disconnect, device number 9
[16627.125468] usb 2-5.3.5: reset high speed USB device number 10 using ehci_hcd
[16627.309145] usb 2-5.3.7: reset full speed USB device number 11 using ehci_hcd
[16627.512684] usb 3-1: reset full speed USB device number 2 using uhci_hcd
[16638.426057] gnome-screensav[2108]: segfault at 5 ip 00007f5e47fda859 sp 00007fff7fe06690 error 4 in libcairo.so.2.11000.2[7f5e47fa1000+b9000]
[20241.656554] gnome-screensav[8820]: segfault at 5 ip 00007fad73a01859 sp 00007fffd2f02b10 error 4 in libcairo.so.2.11000.2[7fad739c8000+b9000]