The microblocks.cfg for Blightfall has a simple typo that prevents Underground Biomes Constructs stone brick blocks from being used with saws in microblock recipes. The bugged line is numbered 11 and reads: "UndergroundBiomes:metamorphicStoneBricks":0-15
Using NEI to dump blocks.csv the relevant id for UBC stone brick is: "UndergroundBiomes:metamorphicStoneBrick"
Removing the s fixes the problem. The problem is identical in the igneous rock entry as well.