This is not a BUG : this is an incoherent behaviour.
Tested with firefox (1.0, 1.5) and ie6.
Safari shows URL in any case.
Other browsers not tested

onmouseover = myfunction
if myfunction ends with "return true", the event should be handled by browser and URL shown in status bar.
here you can see that instead "return false" should be used...i'd like to understand what's the logic !
This is without event handler : mouse over me !

But if i put the anchor in (let's say) a <P> on which i set

var Fdiv = document.getElementById("div2");
Fdiv.onmouseover = test2;
function test2(e) {
	// do something...
	return true;
}

It doesn't work any more :

That one should SHOW THE URL
function test2(e) {return true;}

I expected this case NOT TO SHOW THE URL
function test1(e) {return false;}

This one is for reference
function test3(e) {return;}

Conclusion : on should not use handler return value (false or true) to stop or propagate onmouseover event...

Contact : jerry AT edagames.com