This is a restatement of a previous JIRA, following instruction from Sidewinder Linden to open new item if problem is still there.
Simple small physics enabled disk sinks in Havok4, it did not in Havok1. This despite having a buoyancy set at 1 and a hover height set to be the height it was rezzed at.
The problem can be overcome by adding 2 metres to the hover height, but then preceding push actions cause the disk to slowly rise to a height of 2 metres above the rezzed position over the tau for the hover height.
This effect occurs on other peoples computers with different and newer environments.