I did not had this problem before.
When I put that Dense support to be more than 0 (, program goes to "Looking for overhangs.." error and 100% CPU usage.
I am using this option almost every day, but did not have those kind of problems.
There are at least two threads on this. viewtopic.php?f=9&t=4789 viewtopic.php?f=8&t=4505
Some models have sliced if I increased the layer thickness. I've also made some coarser STL files to resolve the issue. That was eariler before I ran into the same thing you did - dense support layers. I've never had to go down to zero on my models though.