I don't know if other people are having this problem - but compiz does not seem to shut down when I exit Ubuntu (Obviously Narwhal is very early in the developmental process) - Like many people I had a real problem with the panel "max,min and exit" disappearing last week - however it seemed to be corrected by stripping out compiz and nvidia drivers and then updating.
Yet one of the bug that preceded not having a (X-windows desktop?) functioning computer was this recurring thing about a programme not being able to shut down.
There is no crash report the I can file - but the problem seems to be consistent.
I have used this as a testing/learning process - so my machine is probably is loaded with old files and propriety files (Dropbox and Nvidia).
I upgraded from Karmic to Lucid to Maverick to Narwal and have always bkup data so it not a loss to re-install - I was interested to see what went wrong along the way!
One thing I tried was enabling "Unity" but it gave me a desktop with no access to programmes (again last week when I was trying to problem solve).
If anyone has comments on this hangup when compiz seems to stall on shut-down I would be interested to hear.