OSX10.4 mousewheel not received

So, I’ve successfully compiled my plugin for all platforms… But I noticed that on 10.4, the mousewheel is not received by the knobs, although on 10.6 the exactly same plugin DOES receive the mousewheel. Does this maybe have something to do with the fact that I use 10.5 as Base SDK and the deployment target is 10.4?

Could be.