I think most users of Mozilla Firefox 3.6.10 have problems with o error immediately after Installation the browser. The installation package of Mozilla Firefox, comes with add-on-ul Default Manager (v2.2) (developed by Microsoft), which for reasons of security has been withdrawn by Microsoft.
“Firefox has determined that the following add-ons are known to cause stability or security problems: Default Manager v2.2“

Default Manager, v2.2 for Firefox. Reason: security issue, blocked at Microsoft’s request (http://support.microsoft.com/kb/2430460)

If it is a risk for the Mozilla Firefox browser, we do not understand why this add-on was not removed with the release of the latest version.
How can we get rid of the crash caused by the Default Manager (v2.2) add-on in Mozilla Firefox.
1. After installing and opening Moziila Firefox, go to Tools > Add-ons and in Default Manager 2.2 we click on “Disable”.

2. After deactivating the add-on, click on the button “Restart Firefox“.
Default Manager 2.2 – Disabled for your protection.

Probably in the next version of Mozilla Firefox, this add-on will be removed from the installation package. Until then, this add-on will stress enough users. Let's hope that the new version of Firefox, Firefox 4.0 which has reached Beta 6, will be released as soon as possible.
Fix Error / Crash in Mozilla Firefox – Add-on Crash .