In IE the Ruler widget accepts the double click to end the digitized rule line.
However, when doing the same procedure in Mozilla or Netscape this is NO
reliable, maybe %10 of the time the double click works. 

Other weird things also occur if the user right-clicks on the map then go back
to digitizing the rule line.

Possible solution is to base the end-node of the digitized line by two or three
clicks on current node position, and not define the end-node by time between
clicks on the current node. Different browsers many have different times for
clicking, making it more or less sensitivities between browsers.