Assuming that in cudaMiner debug mode (-D) "hash <= target" entries are indicating stale blocks, do I need to worry about "hash > target (false positive)" entries? I'm having a lot of them in pool mining but obviously there is no wallet debug in that case to figure them out.
cudaMiner:
[2014-01-06 17:33:59] DEBUG: hash <= target
Wallet debug.log:
2014-01-06 17:33:59 proof-of-work found
hash: 000000036f84eb900122146301c4e0a6941ad0da6b8947037b42723d76de49c7
target: 00000003b9e40000000000000000000000000000000000000000000000000000
(...)
2014-01-06 17:33:59 ERROR: generated block is stale
"hash <= target" is a good thing, meaning that your cudaminer completed some work.
"hash > target" won't occur a lot with the current github version. It means the hash was close, but not quite acceptable.
"ERROR: generated block is stale" is a bad thing meaning that the work that cudaminer has been doing was valid only for an outdated block, and the hash is unsuitable for signing the current block. Either because a new transaction was added to the current block, or because someone else found a block before you did. The longpoll support in cudaminer was designed to reduce the chance of this occuring. I think a short -s parameter in the range of 5s also reduces the chance of such a mishap.