I think I'm on to something: the problem seems to be with the "click-drag-release" drawing option. Going to "auto detect" and "click-drag-click" I was able to draw lines. I find "click-drag-click" to be a bit of a "drag", so to speak, but the "auto-detect" option seems nice, although I'm not sure what to expect with that option.

Mine is an iMac 4,1. I tried the preference change you suggested and, on a new screen, the problem still exists. I do not have this problem with Sketchup 7 on my old Powerbook laptop which does not have Leopard. My preference is to work on my larger-screen iMac, but cannot do so if the line tool does not draw lines....

Try as I may, I cannot use the line tool successfully with Sketchup 7 and Leopard. I've tried re-downloading and installing Sketchup 7, all to no avail. Sketchup is virtually useless without use of the line tool. My cursor lights up the starting and ending points with the line drawn, but when I click the mouse, the line disappears.

Lee