OrionProject, if you don't have the Auto Layout Presets folder, that could be causing the problem for you. Those presets should have installed when you installed Lightroom 4. Perhaps try re-installing, just to see if they get created.
The presets folder is the same between LR versions, done that way so you can continue using your favorite presets as you migrate versions.
Everyone else, thanks for the quick responses. Go ahead and change your preference back to store presets in the usual location - I think you've proved that isn't the cause.
The next step to try is to weed through existing presets to see if any of them are causing a problem. Here's how I'd like you to do that.
1. Exit Lightroom
2. Uninstall Lightroom 4 Beta.
3. Move your existing presets folder to a different location.
4. Reinstall Lightroom 4 Beta.
5. Start Lightroom, and see if you can switch into the Book module.
If you can, that means that LR4 is choking on a preset you had existing prior to installing the Beta. If this is the case, precede with the following steps.
6. Quit Lightroom
7. Go to the presets folder you moved in step 3.
8. Pick one folder, drag the presets from that folder into the folder of the same name in the real presets location (which should have been created when you re-installed LR4 Beta).
9. Start Lightroom and try to switch modules.
10. repeat steps 6-9 with each folder until you run into the module switching error again.
If you can narrow the problem to a specific preset or set of presets, I'd be interested to get those preset files for further investigation.
Thanks,
Becky
