I have a hier block with a couple of message i/o and complex stream i/o. After including the hier block in a top_block and running, it threw out an error about input ports being out of range. It turned out that it had assigned a port index to a message input, so the stream input had been displaced to higher indices that didn't actually exist in the io_sig.
As a work around - I deleted all of the pad sinks/source in the GRC file, added the stream sinks/sources, and then messages, to assure that the hier block generator assigned stream ports to the lower indices. [ I was a little surprised this worked actually].
I can try to track down the cause, but I thought I'd mention it here if someone knew exactly where to look.
Or maybe I'm just doing something silly?
-John