A superblock is just a block that contains extra information updating how the proof-of-research rewards should be distributed. If it's late, solo miners who joined since the last update can't get rewarded until it shows up again, and the reward distribution is a bit "unfair" until then since some people may be paid more than they should and others not enough.

It primarily exists to avoid reliance on central statistics servers and that's where it gets complicated; since there isn't a central server, all the various nodes have to agree on what the current statistics are, and that agreement is the superblock. With all the increased competition due to new miners jumping on in the last month or so, some bugs and inefficiencies are showing up. This is actually a good thing insofar as fixing these issues will make sure we can scale once the team requirements are removed, since we expect that growth spurt to dwarf anything we've seen yet.:)

It should be noted that it doesn't affect the security of the blockchain at all, nor does it affect people running in investor mode. It also doesn't really affect pool miners as much, though the pool as a whole may not get as many rewards as it should if the superblocks are delayed too long.

I expect we'll see a few more delayed superblocks until it's sorted out, but I'm pretty confident that our developers will come up with a good solution.:)