I have been periodically having this problem. I upgraded about a year ago from Version 16 to 2012. I have been cleaning up my sources and places. I had a lot of locations with slightly different names. I have been combine them into one and making any corrections to the fact in each of the people in the tree as needed.
Periodically FTM will disappear with no messages. I thought that it was a memory problem but increased the memory form 1gb to 1.5 gb, and it did it again last night. Last night it seemed the the program was still loaded even though it did not show in the task Manager.
Windows XP SP3 dual processor 1.3mh. *.ftm file = 13.3mb