I've seen several mentions of an issue when running tests in Firefox: the Flash player doesn't load the SWF if the browser window doesn't have focus. This causes sporadic test failures if the system used for running tests is doing anything else. I've verified that if the Firefox browser is behind IE the test will hang until it times out or else I bring Firefox to the foreground manually.
A workaround that allows the Selenium2/WebDriver test to bring the browser to the front or to override this behavior of the player would be much appreciated.
I've copy/pasted this answer from the webdriver groups.
Hi, The focus thing is a real problem for Firefox (in particular) and becomes even harder when tests are run in parallel for obvious reasons.
Is this something that other people have been struggling with too?
Another thing you could do is to use a tool like desktops to make sure your browsers are opened on their own desktop. If you use selenium RC just start RC from the desktop you want your browser to open on.