From time to time when I am modeling I will make a drastic change early on in my design that results in a few features that need to be updated. The "pink dot" is often due to these types of changes early in the model where features can't locate the edge or vertex they previously were referenced to.
Chances are there was a change made that removed an edge or vertex that has caused a projected point to become sick. In the past you needed to delete all the line segments that were constrained to this reference point to be able to delete the actual point to clear this issue up.
With some of the constraint changes in Inventor 2008 this is a simple fix. While in the sketch, right click and select Constraint Visibility. From here you can filter out all constraints other than a new constraint type called Reference.
Now just locate the reference constraint that belongs to the sick point and right click to delete the constraint. This should remove the pink color and error message for the particular point that was sick. You might need to repeat these steps if you have more than one sick constraint.
Notice the point is no longer sick.
I hope that is a little tip that will save you a bit of time in the future if you run into this issue.