Hi, I'm not certain about Vista 32, but later posts are on OSX.
I had exactly the same problem, missing strokes, I did tests where I used the 'tally counting' type IIII plus a / through them to see how many it was missing - so sets of five multiple times, sometimes it was missing as many as four out of five.
What I discovered was that this did not happen with photoshop - lag, yes, but no missing strokes. I am using a Cintiq not an Intuos, but the same might be true.
I found that the driver that is not supposed to work with Snow Leopard works fine, the new Wacom driver causes more lag and missing strokes. There are three 'post Snow" drivers, which get gradually better, but still missing say 2 in five strokes.
So, For Mac users, chuck out the new drivers, revert to the 32 bit pre SL drivers and I think that may solve it for you. Perhaps for Win 32, look for the older drivers also - all on the Wacom site.
Autodesk by the way seem to sell the SketchBook Pro software diret, but them provide zero support for it. They just passed me on to a line of folks, distributors etc in the UK that ended with a reseller who didn't sell me the product - so of course wanted to be paid for asistance. Seems the Autodesk way is to get users to do the supporting - like this - doesn't cost anything then and they can keep the focus on profit margins.
Stephen