[Problem] FF.au3 _FFClick doesn't work properly

[4ggr35510n]

HTML code of the element i want simulate click on (viewed with firebug):

<input name="submit" type="submit" onload="this.disabled=false;" value="OK" style="font-size: 10pt;" />

I want to simulate click with this ff.au3 function:

_FFClick("submit","name")

And it doesnt work :/

Console returns:

__FFSend: try{FFau3.simulateEvent(FFau3.WCD.getElementsByName('submit')[0],'MouseEvents','click');}catch(e){'_FFCmd_Err';};
__FFRecv: -3
_FFClick ==> No match: $sElement: FFau3.WCD.getElementsByName('submit')[0]

So I try again, diffrent way:

_FFClick(_FFObjGet("submit","name"))

And still doesn't work, console returns:

__FFSend: try{window.content.top.document.getElementsByName('submit')[0]?1:0;}catch(e){'_FFCmd_Err';};
__FFRecv: 1
__FFSend: try{FFau3.simulateEvent(FFau3.WCD.getElementsByName('submit')[0],'MouseEvents','click');}catch(e){'_FFCmd_Err';};
__FFRecv: -3
_FFClick ==> No match: $sElement: FFau3.WCD.getElementsByName('submit')[0]

What the heck? _FFObjGet returns "1", so this element/object exists.

Why FFClick on this existing element/object returns error -3?

Please, help me.