I don't think the attachment 2 posts above will do any good with 10k resistors.

I had actually started making a flash demo for this when it first started, but with so many options it got too complicated.
I really think the correct theory is in the link from post #13 though. The link is also in the flash below ... under the title. (batsocks.co.uk/ ....)

I only made it through simulating +5V. Things are clickable in the image below ... try it.
At +5V the resistor is 100 ohms (with 2 diodes).
But if your situation is different, perhaps I can add to it. ...

<OBJECT CLASSID="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" CODEBASE="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,40,0" WIDTH="723" HEIGHT="800" ><PARAM NAME="MOVIE" VALUE="http://www.pbpgroup.com/files/2LED/2LEDS_1PIN.swf"><PARAM NAME="PLAY" VALUE="true"><PARAM NAME="LOOP" VALUE="truSe"><PARAM NAME="QUALITY" VALUE="high"><EMBED SRC="http://www.pbpgroup.com/files/2LED/2LEDS_1PIN.swf" WIDTH="723" HEIGHT="800" PLAY="true" LOOP="true" WMODE="opaque" QUALITY="high" TYPE="application/x-shockwave-flash" PLUGINSPAGE="http://www.macromedia.com/go/getflashplayer"></EMBED></OBJECT>
Oh, it says I attached the .dsn file ... I didn't, cause it wasn't done.
But if you have Proteus, I will make it work for all conditions ...