I have a problem with using the newly inroduced weka-optionhandler-setting. When I try to override any setting using a flow variable I get the following error "Unexpected error while loading settings from class: weka.classifiers.lazy.IBk, using default values" - this particular one is for IBk while trying to override the K parameter value (which, for some reason is reported to be of string type).
Interesting, it seems to work for me although I see what you mean about the type of K. What operating system are you using?
I'm using Windows 7 x64, what I was trying to do, was optimizing the K value with the use of parameter optimalization loop.
I've also noticed that WEKA3.7 classifiers won't work if the predictor's input table doesn't have the class column.