OK, so setting up and maintaining Knowledge is a big job. Adding alternate languages to it makes it even more complex. Now try combining that with a few brands on a few different public sites and it's quite a handful. 

Some notes on translations. 

As per regular knowledge, permissions are key. If things go wrong, it is usually in permissions. 

Settings

Permissions

https://help.salesforce.com/HTViewHelpDoc?id=knowledge_setup_users.htm&language=en_US (this is a helpful article). 

Publishing

https://help.salesforce.com/HTViewHelpDoc?id=knowledge_article_publish.htm&language=en_US

Start in the Article Management Tab rather than the Knowledge Tab.

No, I don't know why there are two tabs, it is very weird. (Ok, it's to do with KCS stuff - read the whole KCS section in here https://ap1.salesforce.com/help/pdfs/en/salesforce_knowledge_implementation_guide.pdf)

Translations have a different life-cycle to the actual article. 

Finding Translations

This is weird, the translation management is in a different tab to the article management. I guess it makes sense to someone. 

Editing Articles with Translations

So you want to make one sentence change in the English article. I would do everything in the Article Management Tab

All that seems pretty ludicrous if you are doing this all yourself. It is less silly when you are in a large team and it is someone different's responsibility to publish articles than translate them. 

Public Site

I'm (unfortunately) using Public Knowledge for Mobile, Web and Facebook, but thankfully one of the things it is good at is managing translations. Just set your Public Knowledge Base to allow for multiple languages and the Language switcher will appear on the page, and will switch to the desired language. 

Notes

My client has in-house translators, so I am not having to worry about exporting and importing translations. Let us know in the comments if you have done this and what the gotchas are. 

I'm also not using approval processes etc, and the translators are the knowledge managers also, so my notes are very simplified.