Jim&Tonic,
Depending on the visual layout of your slide (whether or not you're doing a
traditional black screen with lettering), you could anternatively animate a
textbox using a top motion path. I'm not sure off hand what the height limit
of a text box is in PowerPoint, but it is significantly more than 25 lines.
You will need to zoom way out to be able to set the motion path to an
appropriate length.
If you have a very long list as it sounds you may need to manually specific
a time greater than "very slow" on the animation speed. To do this,
right-click the animation on the Custom Animation window > Timing... > in the
spped window type a time like 20 to indicate 20.0 seconds.
HTH
Cheers