Black dots/lines on i9900 prints

My i9900 has been making icky black lines on the trailing edges of
prints. According to the canon interactive troubleshooter, this can be
avoided on small prints by bending the paper away from the print-side
before feeding it into the printer. I've tried this and it reduces the
appearance of these streaks considerably.

It also says that for larger prints, there's nothing you can do about
it, which really annoys me. When I print out a borderless 13x19, I
don't want there to be streaks on it.

I wasn't using photo paper pro, but a third party paper, so maybe
that's the cause.

Has anyone else seen this on their i9900?
Here are a few photos that've come out with streaks/spots:

http://staff.washington.edu/jscoles/images/canon/

The full-size versions are what I sent to the printer, the small ones
are crops that I scanned from the printed versions.

Notice that one photo has a row of black dots on the bottom (right edge
while printing) of it. Canon's website doesn't mention this problem,
so could this be an indication that something is wrong with my printer?

Niether of these problems happens all the time, but they do happen very
frequently. (1 in every 2-3 prints)


Canon's info:

Category : Print quality problems
Description : Streaks or lines are printed, or printing is uneven.


CD
03RQ01447_EN_03

Streaks or uneven printing on the trailing edge of the paper
On the trailing edge (approx. the final 2 to 3 cm (inside the red
frame) ) of printed paper, streaks or uneven printing may appear.


Direction of paper movement in the printer

How to avoid appearance of streaks or uneven printing when using 4" x
6" sized paper

1. When printing on paper, set it in the printer after bending it in
the opposite direction, as shown below.

1) Set a sheet of paper on the printing side of the paper to be printed
on.
(If the print surface is touched by hand, the print surface may be
soiled by skin oils, and the print quality may deteriorate.)

2) To bend the paper, hold the paper in a rounded shape for about 10
seconds.

3) Remove the paper not to be used in printing, and confirm that, when
laid flat with the print side up, the center of the paper to be printed
on is raised between 2 to 5mm.

4) The curled paper to be printed on should be set in the printer, and
printed, sheet by sheet.

2. Use Photo Paper Pro PC-101 4" x 6".
Using PC-101 can prevent appearance of streaks or uneven printing, as
printing is performed only in the center of the paper.

How to improve the print quality when printing on A4 or Letter-sized
paper

When using A4 or Letter-sized paper, printing is performed outside the
printable area. Therefore, avoiding the appearance of streaks and
uneven printing is not possible.
However, under conditions below, streaks and uneven printing become
less visible.

Paper used: Photo Paper Pro PR-101
Print quality settings: High or Fine (after clicking Custom)