[gutsy] weird, two running Xorg Sessions, but only one is active

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Hello 

In gutsy I just found two Xorg sessions running at the same time. 
(I didn't start gdmflexiserver or another second Xorg at all)

- I started an ordinary GNOME session with gdm. 
- I didn't edit the GNOME entry for gdm so it's the original file wich comes
  along with apt
- I haven't installed xgl atm (purged it some weeks ago)

- A 'pstree -p' shows:
  |-gdm(5171)---gdm(5172)-+-Xorg(5178)---Xorg(5350)
  |                       `-gnome-session(7578)-+-...
  |                                             |
  .                                             .
  (.) I cut the rest 

- So the second Xorg (pid 5350) is idle but according to top it consumes the
  same ammount of ram:
    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND 
   5178 root      15   0 75260  37m  11m S  0.7  3.7  12:12.08 Xorg
   5350 root      19   0 75260  37m  11m S  0.0  3.7   0:00.00 Xorg

  Or am I misinterpreting the output of top here, I don't think so?

- Killing Xorg (pid 5350) frees the used ram and shows no negative effect.

- Anyone else who may confirm this behaviour in gutsy?
  (last upgrade here was Fr.14.09 10:00 UTC from de.archives.ubuntu)

- Any idea how this might have occured?


regards,
thomas