lag in typing

[Walnut Crunch]

I'm using the latest version of outliner pro on a G4-800 and when typing it
has become very laggy.

It used to be really crisp but now there is a discernable annoying lag when
I type.

The lagging document is about 3 pages long with a number of bullet points
and lots of notes for each bullet point.

I've also used semi transparant colours to highlight different bullet
points.

Is it the colour that is slowing down outliner or something else?