Firefox Initiation

My firefox 1.07 has developed a minor opening problem. If I click on the desktop icon to start, it flickers and the hour glass comes up and then it stops. The start page does not appear but Firefox THINKS it has, because if I try to re-install it, a message says close current firefox programs prior to installing.
Yet there is no firefox in Task Manager, so I have to proceed saying it's OK to close the non apparent Firefox and re-install. This doesn't always happen, but about 75%. There is obviously a not right file somewhere. Anyone expereienced this?
phantazy