Could not commit changes

When I want to install a package I get a pop up window with the following message:

There was an error committing changes.Possible reasons include problems downloading some of the packages or that the commit would break other packages.

Before that message I encountered the following message:
You will not be able to change your system settings in any way (install, remove or upgrade software), because another process is using the packaging system database (probably some other Adept application or apt-get or aptitude). Please close the other application before using this one.

After cheking with ps -ef | grep -i adept, there were nothing related to a running adept process.

I run: aptitude update and then dpkg --configure -a, and since I have the 1st message.

Best Regards,