Looks like there are issues with charts and Google Chrome (18.0.1025.142).
Using Firefox everything looks like with ExtJS 4.0.7 (see screenshots).
When I use Chrome, in my example, the red line (which is based on a line chart that uses a specific marker config to display those lines, see code) is missing, which however worked with ExtJS 4.0.7.
BTW maybe the way, I'm doing that is clumsy and there's a better way to display those limit lines (the red and blue one).
Bildschirmfoto 2012-04-05 um 12.22.16.pngBildschirmfoto 2012-04-05 um 12.26.46.png