it sounds like there's something up with your table settings. i have a Wacom and you can choose if you want to use only a limited area of the tablet or the whole thing. I suggest looking around in your tablet settings and if you can't find the answer there just restore them to default. Good luck! I hope this helps!

Can you move the tablet cursor out of the quarter then you use windows standard Paint program?

No. As long as OpenCanvas is the active program it treats the top left quarter of the tablet as if it were the entire drawing surface. If I go beyond that quarter it just presses the cursor to the right side or bottom of the screen

Hmm... And it doesn't when OpenCanvas off?
That is puzzling. It dose sound weird if it only dose it then OpenCanvas is on.
But if you have another program that can use intuos3 tablet like Adobe Photoshop try it there, while OC is closet.
If it dose the same there, try reset the tablet settings or perhaps upgrade the driver fore the tablet, from Wacom website.
But if not, then try to move OC to a new folder. It mind help.

No dice. Neither updating my drivers nor moving OC had any effect. I also tried installing version 3.3, only to have the exact same problem

Are you using a multi-monitor setup? I had problems with mine, and need to disable my second monitor to get OC to work correctly.

No, I only have one monitor

Well then there only one thing left I can suggest and is to go in too the register delete OC current settings.
That be done by "run" regedit and look down the registration path HKEY_CURRENT_USERSoftwareportalgraphics and delete the openCanvas data folder with all its contents.
When you open OC again will do so as if it was the first time it was opened.

BUT! If you not sure on that I'm saying here please be say it, because this the core of windows and can cause damage to the system if not done right.

I mean Registration path HKEY_CURRENT_USER Software portalgraphics ^^

Open your tablet settings while oC is open and make sure it doesn't have inddividualize settings that are causing a problem. In general oC has various odd hablet quirks though, out of no where mine started treating the mouse the same way it treats the pen.

Sorry, ive only just got those two things and it works perfectly for me, ^^ but good luck trying to fix it and if you do i would love to OC with you ^^