I'm not yet sure how to replicate this, but sometimes Tolk::Locale.dump_all stores a translation as a zero (integer) in the YAML file. Editing the text in tolk admin via Textmate then dumping to YAML resolved the issue, but it recurred. Has anyone else experienced this? I'll update this ticket when more info becomes available.
Please repost here github.com/tolk/tolk if this issue hasn't been fixed (by the yaml engine update ?).