Is your Electrolyzer running properly? With enough EU/t? Seriously, you need to be VERY careful about what you do with what Voltage. This isn't as baby simple as IC2 with the Tiers.
I mean, it is working with other dusts correctly. It produces all purified/impure dusts correctly and most of clean dusts, but some (like silicon dioxide and others, I can make a list) just don't want. EV electrolyzer connected directly to MFSU.