I would have thought that you should have more restore points than that.
Click on the box for Show more restore points to see if it gives any more.
If the bug is related to the program then no amount of fiddling is going to resolve, but in the rebuild icon link I'd posted, clicking on the hyperlink in there for restore default file extension's associations gives you several registry batch files for restoring those, but as usual, create your own restore point before making any changes to the registry.