Have you tried to perform a clean installation? Such IDE starting error can usually fixed by removing Lazarus with all its configuration files and install again.
You can use the commands as suggested by Thaddy in this thread:
http://forum.lazarus.freepascal.org/index.php/topic,33525.0.htmlAlternatively, I prefer to use Synaptic Package Manager to perform complete removal and installation. This is a handy tool, it can show you dependencies and broken packages which hinder some application to install correctly.
Or perhaps you can try to obtain the installation files directly from Lazarus download link:
http://www.lazarus-ide.org/index.php?page=downloadsYou need to download and install all three packages as mentioned on the download page.
I ever experienced application that won't be able to installed on my Ubuntu Mate pc even I follow the instruction correctly. But a simple computer restart fix the issue.