Frequently, Area Miner fails to activate correctly in 1.8. The block being mined will become invisible and not drop anything (a state often seen in vanilla when mining dirt with high efficiency shovels). The surrounding blocks may or may not be mined (can't remember), but usual are not mined, or are made invisible, as above.

Occurs:

• Mostly with blocks harder than stone, such as ores, granite, etc.
• In both survival and creative mode.
• With both fast and slow pickaxes (haven't tested other tools).

Cause unknown at the moment. If anyone else has experienced this issue, let me know if I missed anything.