Delete duplicated custom fields

I have a site where I rely heavily on custom fields. Somewhere along the way my custom fileds have been duplicated, for example, I have a custom field called ‘age’. This custom field has been duplicated 17 times with the same value in each of them. It might have to do with some of my plugins that I had but I now is trying to clean up my database.

I found a plugin that should clean out duplicated custom fields called ‘Custom Field Taxonomies’ but this seem to clean out a bit too much as I loose lots of posts.

So my question is, anyone have a clue how to delete duplicated custom fields from a database or WXR file. I have about 500 posts and don’t want to this manually ??

Thanks in advance,
/Jens