I still use Processing 1.0.1 but saw nothing related in the release notes.
French Windows XP Pro SP3, Java 1.6.0_13

When I write a simple code without setup(), if there is a syntax or runtime
error, the highlighted line of off by one.

Example:

size(500, 500);
PImage img = loadImage("E:/Documents/Images/lines.gif");
PGraphics pg = createGraphics(img.width * 2, img.height * 2);
pg.image(img, 0, 0, img.width * 2, img.height * 2);

image(pg, 0, 0);

The error is on createGraphics but the loadImage line is highlighted.
If I add JAVA2D, I have a runtime error with the empty line above image(pg,
0, 0) call which is highlighted.

I have a remark on the runtime error, but I will overcome my laziness and
make a new bug report... :-)

please check with the more recent releases--there have been many fixes to
this over the first several so it's likely taken care of.

is there a problem with 1.0.4 that's preventing you from updating? (if so,
please post a (new) bug for it so that i can fix it!)

found and fixed in svn, and for whatever comes after 1.0.6. thanks for the
report!