KNOWN ISSUES WITH v3.1 (Pre-release Build 4345 - Dec 2011):
If you open an .otf or .ttf file that has OpenType Layout tables with TypeTool 3.0 or with FontLab Studio 5.0.x, save the file as .vfb, and then open the .vfb file in TypeTool 3.1 build 4345, the name tags of the stored binary OpenType Layout tables will be reversed. If you then go ahead generate an .otf or .ttf file, the OpenType Layout tables will become unusable.
Note: this only happens if you open a .vfb file in TypeTool 3.1 build 4345 that was previously saved in TypeTool 3.0 or FontLab Studio 5.0, and only when originally, that .vfb file came from opening an existing .otf or .ttf font file. This problem does not occur if you open the .otf or .ttf font file in TypeTool 3.1 directly, or if your .vfb was started from scratch. And the problem only affects stored OpenType Layout tables.