I'm not entirely sure, but I think you got this line wrong:
var seekTime:Number = (mouseClickedXPos-100) * (totalTime/(controlBarControls.width-100));
Try this instead:
var seekTime:Number = ( ( mouseClickedXPos - 100 ) / ( controlBarControls.width - 100 ) ) * totalTime;
Basically, you were comparing two completely different quantities to form a ratio and multiply that by the mouse click position. Instead, divide that mouseX by the total width (giving the position of the click as a percentage of the total width) and multiply that by the time (giving you a percentage of the total time).
I'm not overly familiar with the way NetStream works (I've used it, just not extensively enough to know this off the top of my head), but if you pass a time greater than the totalTime, there has to be an error or it has to handle it by either not completing the command or by setting the value to 0 (which I personally think is what would happen. It's how I would do it, at any rate)