To reproduce: * Inspect an element * Close the inspector (with the "X") * Go to a new tab (or an existing tab) * Return to the original tab Now the inspector will be open again, as though it was never closed. Going to a new page stops this behavior.
You're claiming this is in 9 branch, is that accurate? (Beta?) It was fixed in bug 690361 which is targeted at fx 10. Since this is preffed off for 9, I don't think we'll be able to land it on branch. :(
I encountered it on 9.0a2 (2011-10-17) (Aurora)
I just tried this in Nightly and Aurora and this appears to have been fixed sometime in the last two months. Setting target for Firefox 10, since Aurora seems good.