Devs,

1. Thanks for getting us over this glitch safely.

2. It is beyond belief that validity of a block could be decided by such implementation specific matters like BerkeleyDB record locking.
And, of course, there is no specification of what is a valid block. The code is the specification? So make no changes to the code and we won't have forks?
Please take the code at some point and write the specification of what is a valid block. Then change the code as you like and test if it's ok with the specs.
Also you may find out that the block validity rules are too weird and could refactor them better.
As Mike Hearn says, money could be lost here.