Could someone please prove my following maths wrong:

hash_rate = (blocks_found/expected_blocks*difficulty * 2^24 / 30)

I looked at the block window from block 456520 onwards (approx 2013-12-14 20:10:18 GMT)
Lets look at a 5 minute window, which should get us 10 blocks.
Depending if we start this window at 20:10:00 or 20:10:18 we get 10 or 11 blocks "solved" in that time, so lets take the middle and take a factor of 1.05

So we have:

hash_rate = 1.05 * 6411.26760900 * 16777216 / 30
hash_rate =~ 3764712752 =~  3,76 GH/s

So we have approximatly a network hashrate of 3,67 GHashes per second.

http://qrk.coinmine.pl/ showed at that time an approximate pool hashrate of 3,8 GH/s.

So either my maths are totaly wrong, the pools hahsrate display is totaly wrong, or houston, we have a very big problem...