Same problem here, with Ubuntu 13.04 on an HP Pavilion dv3 laptop, with ATI graphic card (using ATI non-free driver).
The command provided by Bryan Mullan (i.e., gsettings reset org.compiz.core:/org/compiz/profiles/unity/plugins/core/ active-plugins) worked for me (Thanks Bryan!).
Same problem here, with Ubuntu 13.04 on an HP Pavilion dv3 laptop, with ATI graphic card (using ATI non-free driver).
The command provided by Bryan Mullan (i.e., gsettings reset org.compiz. core:/org/ compiz/ profiles/ unity/plugins/ core/ active-plugins) worked for me (Thanks Bryan!).