hi, thanks for reporting this. could you go to the firefox ''menu ≡ > help ? > troubleshooting information'' page and take a look in the ''Accessibility'' section if accessibility is set to "true" there. if yes, can you please copy & paste this whole section into a reply in the forum and see if the following fixes the performance problem: go to the firefox ''menu ≡ > options > privacy & security'' panel and under permissions check the setting to '''prevent accessibility services from accessing your browser'''.