** Dan’s comment below mine should probably be read first, but I’ll keep this up just in case that doesn’t work. which it probably will.
What workarounds?. . . or at least what were some of the buzz words which were used in them?
As always I agree with jvleearchitect about it likely being an OS issue, and also that a first step should probably include a visit to the mouse preference settings, and then possibly to the mouse drivers to make sure that are updated.
I’m always suspicious of sudden changes being related to incompatible software, starting with drivers, or other updates (including “auto updates” which happen in the background).
Otherwise in terms of taking this search outside of the SketchUp Forum I have found a few interesting articles which might help out, or possibly be familiar to you already.
Here’s a tutorial for disabling the mouse acceleration settings in XP.
I’ll keep this problem in mind and carry on with a little research, reporting back when I can.