MARWES  tell me where I can find such a dictionary and I will add it (please issue an feature-request on the sourceforge-site)  
(Version 0.12.1)

MARWES  Thanks for the log and being so patient.

A new version (0.12.1) is available for download on the sourceforge-site that fixes this bug.

I've updated my list of checks to perform before releasing...  
(Version 0.12)

MARWES  could you please give me more information: crash-report, Version of MacOS X, ...

try to delete ~/library/preferences/translator.plist

if that doesn't help delete the complete app an re-install a fresh copy.

Sorry for the trouble  
(Version 0.12)

MARWES  I'm sorry for the troubles. The reason may be that I changed the way dictionaries are organized from 0.9 to 0.10.

Probably you should delete just everything (~/library/preferences/translator.plist AND the app) and re-install a 'fresh' copy of Version 0.10.1.

Again I'm sorry for the trouble but please consider that versions prior to to 1.0 are explicitly marked as non final.  
(Version 0.10.1)

MARWES  MacTranslator itself is just an graphical interface that allows you to search in freely available dictionaries (like the one on http://savannah.nongnu.org/projects/ding-es-de for example).

Tell me where I can find such dictionaries for the languages you requested and I will add support for them....

Please add a feature request on the sourceforge-site.  
(Version 0.9)

MARWES  I will add new dictionaries as people request them. The problem is to find freelay available ones that reach a certain level of quality...

Please note that 0.9 is a pre-release. For the first final release I'm planning to add a feature that auto-updates the list of available dictionaries.  
(Version 0.9)