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any way I can re-install Firefox 4? Firefox 5 is lacking plug-ins I need

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Would like to return to previous version of Firefox and not use v5

Would like to return to previous version of Firefox and not use v5

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What exactly isn't working?

Due to security vulnerabilities, rolling back to Firefox 4.0.1 is not recommended.

If Firefox disabled some add-ons (especially extensions), it likely is because they include a list of compatible Firefox versions and haven't yet been updated for Firefox 5. If they worked on Firefox 4, there is a very good chance they will work on Firefox 5.

You can force Firefox to ignore add-on version restrictions by (what else) installing an add-on. Then you can test whether the add-ons important to you actually work in Firefox 5.

Add-on Compatibility Reporter :: Add-ons for Firefox

Please report back on your results.