Can you provide a lot more details about what is happening?
Is the problem happening in the front-end or admin area or both? Did it start crashing right after you installed it, or was it after you performed some configuration (and if so, what were you configuring)?
If you're seeing a blank white page, please go to the Global Configuration area and set Error Reporting to 'maximum'. Then, let us know if a more descriptive error message appears.
Finally, if you can access the admin area, disable the JFBCSystem plugin to see if the problem goes away. That plugin will disable almost all JFBConnect functionality, which is a good way to get things going again while we figure out the problem.
Thanks,
Alex