Intuit has responded that they have identified and resolved the issue that caused the problem, and is working on a solution for users who have already lost data.
For those of you who have been affected, we are testing out options for recovering the deleted files. Our recommendation for now is to turn off your computer and do not use it further. If you continue using your computer or reboot, you may over-write the area on the disk where the deleted data is stored, preventing any recovery efforts from being effective.
Intuit has provided a knowledge-base article on the issue, and will be updating users as new information comes available.