Every now and then, I'll get an unhandled exception that causes the game to stop working. Usually it will still let me save, but that's it. However, as I started up a new game playing as the Mortalens, I noticed that every time I tried to click on the Mortalen entry in the galactopedia it gets this exception. Even after restarting the game and checking the galactopedia entry for Mortalen from the main menu, I get this.
Does this same crash also happen when browsing other alien races in the Galactopedia? If so then your problem is likely that Distant Worlds does not have write-access to the following location: C:\Users\[YOURUSERNAME]\AppData\Roaming\Code Force Limited\Distant Worlds\
When browsing alien race topics Distant Worlds needs to write a file with the race characteristics before browsing to it in the Galactopedia.
You could try running DW as Administrator possibly?
But if this only happens for the Mortalen race, then you probably have some corrupted race files - reinstall to fix this.