I will try your suggestion,

Originally i had set the datasource at design-time, then i moved to run time thinking that would be faster, but it was the same.

I thought it was the dataset, but i also used a DataReader to fill an arraylist with a custom class (ID, Name). This is very fast.

But when i set the datasource to the combo, it took a while to load too.

The weird think is that this happens only the firs time i load the form, the second time loads fast.