Just updated Java, bug still exists with jre-7u45-windows-x64, and with jdk-7u45-windows-x64
Commonly seem when the world name is reused. Old world didn't have time to delete and new one used the same folder name as the old which contained undeleted chunks. We're looking at user error.
Just updated Java, bug still exists with jre-7u45-windows-x64, and with jdk-7u45-windows-x64