This is strange. I did not realize DSL looked in resource files except its own.
Is your skin using DSLocaleSelector or DNN's core language selector? The error you showed was while DSLocalizator tries to determine a language and reads the URL. Question is now, what object produced that?
There were some errors in the url produced by DSLocaleSelector in 3.0.5, but nothing that seems to have a relationship with those resource files.
I'm not quite happy with the way I solved DSL's locale selector issue and I would be happy to work with you to come to a solution that works for everyone.
Locopon, we're waiting for a first beta!