Muliple Firefox Processes / Profiles

The FireBug plug-in for Firefox seems to cause problems for GMail. Even if Firebug is disabled for the GMail page itself, after leaving the page, the Firefox application crashes. With Firebug generally disabled, no problems occur. So, I'd like to have an Firefox instance for general browsing, also using GMail, without any Firebug extension and another instance for JavaScript debugging and HTML, CSS design.

Geek to Live: Manage multiple Firefox profiles

The solution comes with a separate development profile ("dev") for Firefox and a shortcut to

firefox.exe -P dev -no-remote

Then I copy the content of the profile directory "...Application Data\Mozilla\Firefox\Profiles\xxxxx.default" into "...Application Data\Mozilla\Firefox\Profiles\xxxxx.dev" to get all my bookmarks and settings into the new dev profile. Now to have a lite-weight instance for general browsing, I start the default profile and uninstall all the development extensions and remove the development bookmarks.