When I have a headline with a link on it and I have that headline's habit
property set to true, org-habit will barf all over my link when presenting
the agenda. This will only happen when org-habit-graph-column is set
something shorter than the full raw text of the link (which is about all of
them).

I ran git bisect on org-mode and found the bad commit to be:

commit 2f5f6e401f187c2db8131cdbc4355b688ce4c55a
Author: Carsten Dominik <carsten.dominik@gmail.com>
Date:   Mon Jan 4 09:58:53 2010 +0100

    Turn off invisibility while constructing habit graphs

    Bernt Hansen reported strange things happening to the display when
    graph tasks are hidden while updating a task in the agenda.

Here's my bisect log:

# bad: [0e370d498b34469a025cdce864fd5c5987bf8050] Fix typo
# good: [a7fb89e9edf59f50294199046e570b4b11bb13b1] Merge branch 'master' of
git+ssh://repo.or.cz/srv/git/org-mode
git bisect start 'origin/master' 'HEAD'
# good: [21ad7f0bef20addfe15fbe3e95d65e6c810d68f1] Fix typo
git bisect good 21ad7f0bef20addfe15fbe3e95d65e6c810d68f1
# good: [0b5d9bf1c62454523b275dd6a6b95bf881580eb1] Merge branch 'org-ctags'
git bisect good 0b5d9bf1c62454523b275dd6a6b95bf881580eb1
# bad: [588a42d4fd2e59e3f69d5a3f9ea00ff3a64f5df9] org-exp-generic.el: Fix
bug with closing bodies
git bisect bad 588a42d4fd2e59e3f69d5a3f9ea00ff3a64f5df9
# bad: [32441cd15150f541d3ba50633cfb9fffc8d3d11a] Fix agenda link opening
bug
git bisect bad 32441cd15150f541d3ba50633cfb9fffc8d3d11a
# bad: [ddcb2be1c8920fabfbca3777cc774ed1ac653a6e] Work-around for formatting
bug with email subject line from wanderlust
git bisect bad ddcb2be1c8920fabfbca3777cc774ed1ac653a6e
# good: [c23ade5d8e4b3cd4f0c4dbe5260cad1f227d2710] Make C-c r C customize
remember templates
git bisect good c23ade5d8e4b3cd4f0c4dbe5260cad1f227d2710
# good: [f266ee62bb8282cc883adea9f26362b2d3b1ab7d] Fix typo
git bisect good f266ee62bb8282cc883adea9f26362b2d3b1ab7d
# bad: [2f5f6e401f187c2db8131cdbc4355b688ce4c55a] Turn off invisibility
while constructing habit graphs
git bisect bad 2f5f6e401f187c2db8131cdbc4355b688ce4c55a

Luke