I wasn't able to reproduce this with 126.96.36.199.1 using the tutorial example E02 which I modified to use a Line instead of a polygon.
Could you provide more details (or maybe contact us offline and send us a test case).
.... However I have encountered some other issues:
mapviewer : 188.8.131.52.1, browser: firefox v22
1- The distance tool doesn't show distance.
2-The scalebar shows incorrect values.
3-When I turn on/off vector layers visibility programatically (e.g. vectorLayer.setVisible(false)) then the LayerControl Object will not update the check marks.
SRID:32639 (UTM PROJECTION)
shapefile and Html link: http://www.mediafire.com/download/wt16z1yh08ngcp4/testCase.zip
import shapefile> create theme> create tilelayer