Version 1911 was commited by steve on 2011-04-09 14:35:08 +0100 (Sat, 09 Apr 2011) Fix in r1725 wasn't quite right and would produce exceptions for particular sized files. The bug has been reported a number of times (or a similar one anyway) but has proved elusive. Thanks to Andy Allan for tracking down the revision where the problem occurred which lead quickly to the fix.