final fix for this issue hopefully
(did i mention i am on European timezone? where is my sleep)

the block with bad timestamp caused a negative value in difficulty calculation
there is now a fallback
github updated
windows client here:
https://mega.co.nz/#!MxAThAIB!QjpNnt5NJQ2d09t3WgKMkGADGo3DqMyuuPO4C1dGQew