Firebug and Selenium: Performance

My favored solution for this is to make a new, separate Firefox profile (run firefox -ProfileManager), and launch your Selenium scripts using that profile instead. It'll be clean of everything except what you put into it. That way, as little as possible from your personal environment will taint your development environment and you'll maintain a clean separation.

I typically don't run tests from the same machine I develop on. If you can setup a separate test machine where you deploy and run the tests, you can keep Firefox, IE, etc, free of plugins/add-ons like firebug that might get in the way of your tests and avoid this problem completely.

Running your tests on a separate machine also frees your dev machine so that you can continue working while your tests are running. I'm not sure about your situation specifically, but think about when you have hundreds or thousands of test cases running, you don't want to be sitting there waiting for them to finish. You want to be able to work while it runs, view the report it generates, and investigate if necessary.

You could try the alpha builds of Firebug 1.4. The activation/suspend model has changed in this version to a simpler model: it is activated when you see the panel, otherwise it is in suspended mode, see http://blog.getfirebug.com/?p=124 for more information.