Whenever I run DOSBox in full-screen mode, there seem to be pixels missing from the bottom of the screen. The display is truncated by 1 scanline without aspect ratio correction or what does indeed look like 1.2 scanlines with aspect ratio correction enabled.

This happens only when I use overlay output mode. All other modes are fine, as is windowed display. Is this a bug in DOSBox or a problem with my graphics card driver? (nvidia ForceWare 71.81 on GeForce 4)

Using Ctrl-F5 to take a screenshot confirms that DOSBox' internal frame buffer is accurate, so it's a display problem, not a simulation problem.