I had the exact same issue. This is Edgy, and XFCE's autostart was trying to launch evolution-alarm-notify itself, though Evolution already installed a .desktop for the very same purpose (cf. "dpkg -S /etc/xdg/autostart/evolution-alarm-notify.desktop").
To fix it: launch "xfce4-autostart-editor" and disable 'Evolution Alarm Notifier" there.
I had the exact same issue. This is Edgy, and XFCE's autostart was trying to launch evolution- alarm-notify itself, though Evolution already installed a .desktop for the very same purpose (cf. "dpkg -S /etc/xdg/ autostart/ evolution- alarm-notify. desktop" ).
To fix it: launch "xfce4- autostart- editor" and disable 'Evolution Alarm Notifier" there.
Hth,
Francis.