Firefox hangs within a second of starting the application.

Firefox now hangs almost immediately after starting. It loads my recent sites in the start page. None of these have changed. I have not added add-ons. After a second or so, nothing responds. I cannot get into settings or even minimize or close the window. The cursor remains a pointer when hovering anywhere over the Firefox window. My computer has not been restart since last time Firefox worked. I have tried uninstalling. The new install did not help. This is on a Windows 10 machine that has had Firefox installed for quite some time.