Load protecting plug-ins to diagnose problems in Rhino.
Sometimes Rhino will misbehave or even refuse to start. If you believe that a plug-in is the cause, or if tech support suggests that this might be the case, then selectively load protect the plug-ins. Try Rhino without these plug-ins loaded and with them unable to load without your permission. This is a good way to zero in on the culprit.
To load protect plug-ins, open the Options → Plug-ins page. There you will see a list of the loaded and available plug-ins. (You can customize the list to exclude plug-ins unlikely to cause problems, for example, Import/Export plug-ins. To make it easier to locate the ones you are looking for, look at the drop down list in the upper right.)
Each plug-in has a check box for load protecting. If you locate plug-ins you want to test, check the box next to each, answer the confirmation question, then restart Rhino. When Rhino starts, it will ask to load the plug-ins rather then load them normally. If you say no, the plug-in will not load and you can test what you were doing when you crashed and see if it still crashes. By protecting and unprotecting plug-ins you can zero in on the one that is causing trouble.
If Rhino refuses to start at all, then try starting in Safe Mode. There is a Rhino in Safe Mode icon in the Windows Start menu > 'Programs' entry for Rhinoceros. Starting in Safe Mode blocks plug-ins from loading. You can then load protect the ones you suspect and then restart Rhino as normal.
Typically, the first plug-ins to load protect are the third-party plug-ins, like renderers, CAM products, and beta software. If you find that Rhino behaves better without all of these, then try enabling half of them at a time to try to locate the one that causes trouble.