On Xubuntu 11.04 sometimes (usually when i use my wacom + gimp + skype) the xfwm4 did not start with the operating system and i have to start it manually from the terminal.
I am experiencing a similar problem on two different Gentoo amd64 computers, even though I am not using wacom, gimp, and skype is started occasionally.
The list of apps that make it through the login seems random. Sometimes xfwm4 is part of those dropped by the session manager, sometimes others.
How can I help debug and/or workaround this?
Also have a look at comments of bug 8070 that should also be marked as a dup of bug 7864.
*** This bug has been marked as a duplicate of bug 7864 ***