Height 469252 of 469572
failed to process transaction
Another try pull_blocks(try_count=0)...
failed to process transaction
Another try pull_blocks(try_count=1)...
failed to process transaction
Another try pull_blocks(try_count=2)...
failed to process transaction
pull_blocks failed, try_count=3
Refresh failed, no blocks received
Once it was after Height 469252 of 469572
Than after Height 469257 of 469576
You don't need to back up the block chain. Back up the wallet files that you use with simplewallet, there are three of them, one with just the base name, one .keys. and one .address.txt. You should frequently do this anyway.