Word often crashes in Mac when i am working with tracked changes, or can’t use Auto-recover. This happens suddenly and can lose me 2-3 hours work. Does anyone have any suggestions?

When i am working with a document with tracked changes, it will suddenly freeze, say if can't auto-recover because the HD is full, and then crash. losing my latest work. It happens without warning and can lose me 2-3 hours work. I close all the other programs so the laptop is not running anything except word and it still happens. It only seems to happen with tracked documents or those with lots of comments. Does anyoen have any suggestions? I have installed Mountain Lion but it was happening before that too.