Alignment with MUSCLE (from GUI) fails

I can't align with MUSCLE. I'm getting this error:
'MSAAlignMultiTask' task failed: Subtask

{MUSCLE run in separate process align 'new.fa'}

is failed: Subtask

{Run workflow schema for task muscle}

is failed: Subtask

{Monitoring execution of workflow schema}

is failed: No workers are ready, while not all workers are done. Schema is broken?

I'm using the latest snapshot (July 10th).