Buds that form, but "dry" up and turn brown before blooming is almost always a sign of too much water. If the soil is too wet, there are no gaps in it for air and the plant will show its lack of air at its extremeties first, in this case, the buds. It can be misleading because the "drying" effect often makes you think it needs more water, which is the last thing that it needs. Geraniums, in general, like to be on the dry side. The good thing is that they bounce backl fairly quickly, once you let them dry out.