I got 6.0.5 to work for me by going into spp file browser and changing it to only look for sigma raw files (.3xf), then selected view thumbnail in one of the default values. It looks like as a prior user, the correct default info for new spp was left in a weird state.
I have been monitoring the two Quattro threads at getdpi. It is looking encouraging over there. The fw fix may address the color issue that would make monochrome an issue for me.. I may give it a try soon.
Gary