Enter /var/lib/dpkg/info
cd /var/lib/dpkg/info
Delete all entry related to crossplatformui
sudo rm crossplatformui.*
Force remove crossplatformui
sudo dpkg --remove --force-remove-reinstreq crossplatformui (Reading database ... dpkg: warning: files list file for package `crossplatformui' missing, assuming package has no files currently installed. (Reading database ... 159448 files and directories currently installed.) Removing crossplatformui ...
Source: http://askubuntu.com/questions/136423/crossplatformui-error