It works! Thank you for your help and keeping me posted!

[quote="pimjoosten"]Because of your reply I figured out that the UI language was still set on Dutch (which it does automatically when I install MM on a Dutch version of Windows). Then every time I start MM it tries to install the Dutch language addon again. After I had set the language to English it does not reappear after a restart. Now I'll just wait for the new language file and the manually install it. Thanks![/quote]
It has just been uploaded, thanks for your patience!

Because of your reply I figured out that the UI language was still set on Dutch (which it does automatically when I install MM on a Dutch version of Windows). Then every time I start MM it tries to install the Dutch language addon again. After I had set the language to English it does not reappear after a restart. Now I'll just wait for the new language file and the manually install it. Thanks!

[quote="pimjoosten"]Thanks again. How do I solve it when it is fixed on the addons site? Do I need to install it manually? But how do I then uninstall the current broken extension, when it reloads every time I start MM?[/quote]
You should be able to uninstall the current extension as you normally would, via Tools > Extensions. It worked when I uninstalled it.

Thanks again. How do I solve it when it is fixed on the addons site? Do I need to install it manually? But how do I then uninstall the current broken extension, when it reloads every time I start MM?

You are right, I've tried it and it does fail. The language file at the addons site is broken, a file is missing in it. I've just contacted Rusty and he should be uploading a new one soon.

Thanks for your response, nohitter151. And nope, it does not work. I get the error "Dutch translation was not installed." when I try to install the language manually.

There are two strange things to note:
1. The Dutch language is already shown as being installed in the extensions section. If I uninstall from there it seems that it is uninstalled, but when I restart MM I get the same error "Language File can't be installed" and the Dutch language is back in the extensions section again.
2. If I hover over an option in the options windows I do get the tool tips in Dutch! The UI is still in English however.

try a manual installation from:
http://www.mediamonkey.com/addons/browse/item/dutch/

Does it work then?

I tried to upgrade this morning from version 3 Gold to 4 Gold. However I received a couple of different language errors during installation. Since I did not need to keep my database I completely uninstalled version 3 and the installed version 4.0.0.1459. I however get the same error messages:
First: "Error downloading language file for Dutch (installation error)". [I translated this from Dutch, so the wording may be different in the original error message].
Then: "Cannot create file C:\ProgramData\MediaMonkey\Locale\nl\LC_MESSAGES\DB.mo."
Last: "Language File can't be installed". This last error is shown every time I start MM.

It is much similar and probably the same as the error reported here: [url]http://www.mediamonkey.com/forum/viewtopic.php?f=6&t=61858[/url]. It is said there that it is supposed to be solved, but it apparently is not.