I have an x86 FreeBSD system (6.2-STABLE) with a Radeon 9200 video card. I use
this to drive the RGB inputs on a UK standard widescreen television, via a VGA
to SCART adaptor cable. For the last year or so I've been using the following
custom mode line to drive the TV at standard PAL-I line rates (625-line 50Hz 2:1 interlace, 576 active lines):

Modeline "1024x576pali" 19.6875  1024 1053 1145 1260  576 580 583 625 composite -csync interlace

Following an upgrade to Xorg 7.3 this no longer works.

The first sign of trouble was that I needed to add a VertRefresh option to
the Monitor section of my xorg.conf file which allowed frame rates of 25Hz,
in order to prevent the server rejecting the on the grounds of "vrefresh
out of range" - whereas previously the server has treated an interlaced
mode on the field rate.

Even though I've been able to make the server accept the interlaced mode as
in range, it no longer displays correctly. The X server thinks that it has a
1024x576 frame as expected, but the actual video output shows the top half of
one field in the top of the display, a vertical blanking interval in the middle,
and then the top half of the alternate field in the bottom of the display (the bottom half of the display isn't output). The bottom half of the frame buffer
isn't output at all.