Looks like
blockchain.info is undergoing maintenance currently. Perhaps that is why blocks are showing up invalid? If Slush is using blockchain.info for verification (as it appears he might be), then this could be causing our invalid block issues.
actually, the first 2 were invalid at a time when blockchain.info was still up.
I wonder what mechanism they are using to pull the data from blockchain.info. If only part of the site was down, say the mechanism that feeds out block information, then it is possible this could have caused an error on the pool. Could also just be Slush's pool having some issues as well. I am very glad this is now fixed though.
Actually, I am rather surprised to see those blocks valid on blockchain.info, then after an outage as orphaned, then later as valid again. What I saw there made me draw premature conclusions...
I would not take if for granted that the pool uses blockchain.info services to decide if a block is valid (on the main chain, not orphaned) or not... AFAIK any bitcoin client can give you that information.
This is very true. I imagine that someone with Slush's knowledge would not be relying on an external service. Good call.