If you haven't done so already, please report this on bugs.winehq.org
Someone has been faster. It was already there: http://bugs.winehq.org/show_bug.cgi?id=18675
HEAP_MakeInUseBlockFree( subheap, pArena ); is the guilty statement.
Could you explain in which cases this might cause a program to fail? I will test those.
Thank you Niklas