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Firefox generates error "Exc in ev handl: Error: Bad NPObject as private data!" when opening new tab or moving to existing active tab.

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Firefox generates error "Exc in ev handl: Error: Bad NPObject as private data!" when opening new tab or moving to existing active tab.

Firefox generates error "Exc in ev handl: Error: Bad NPObject as private data!" when opening new tab or moving to existing active tab.

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Disable "McAfee Site Advisor" extension which was just updated to 3.4.0, which probably took it out of the addons block list.

  • "Ctrl+Shift+A" > find McAfee Site Advisor and use "Disable", and then restart Firefox.
  • Do a Google Search no problem
  • It seems that if you re-enable Site Advisor again, and restart Firefox you are okay. At least you know where to look if you get the error again or Google searches slow down.