Grid Inline Editing with Combo boxes


I am trying to enable inline editing for a grid of entity objects of type Issue. Each issue has a cause represented by the attribute issueCause of type Cause. When editing the row, I would like to display a combo box with a list of existing values. I believe I’ve done everything right except when I try to edit a row by double clicking on it, I get the following exception:

Caused by:$ConversionException: Unable to convert value of type ...entity.IssueCause to presentation type class java.lang.String. No converter is set and the types are not compatible.

I tried to set a converter on the column, the actual combo box but with now luck. Does anyone have an idea.

I found this example: which is supposed to do exactly what I want. I followed it but it doesnt work for me and I always get the same error.