Found the problem: You need to do the following:
mylinechart.setStyle('calloutStroke', null);
or
mylinechart.setStyle('calloutStroke', colorofchoice); <-- if you want a
different color
Eli, I guess didn't fix this for Gumbo either.
Documentation for Flex 3 and Gumbo, as well as the code says it should be
chart.setStyle('dataTipCalloutStroke', null);
which is not correct (see link below)
http://www.mail-archive.com/[email protected]/msg64697.html

