Mine's a graphire3 , but my pen gets jerky as well and sometimes lags.
Usually though it's just my computer doing it, for jerky-ness I have to restart and for lag just scribble around a bit until it finally catches up.
I doubt I've helped at all, but maybe you could try directly contacting someone from customer support? (Sorry I know, bad solution.)

If you're running other programs close them. That's what makes my tablet lag.

It's probably not much help but I tried. :B

Lawl, Vista. When all else fails, you can pretty much bet that Vista is the problem. It doesn't like oldthings at all. Make sure you have the drivers specifically lableled for Vista. Last I checked, Wacom's site had special drivers for it.

What program are you arting in? And how fast is your computer? It could just be a "dis compyuter sux" issue, but I used openCanvas 3.03ePlus on my old laptop whose specifications didn't even match openCanvas's requirements, and it ran just fine. Though if you have a lot of stuff running in the background it tends to jerk around like you say. :U

I have a grappire 2, too, but I don't have line lag problems unless I'm really slashing the tablet. A quick cut across the sensor pad makes it 'skip' and have to interpolate in a very ugly way. It sounds like you have something more anomalous though.

I can only suggest checking your 'processes' and seeing if anything's using an extraordinary amount of memory/cpu time that's NOT the tablet.

I dunno how these things work or else I'd say more ;[

I had a similar problem and i traced it to one of my USB ports.

i had a graphire 2 and it worked fine but i was using 98 and up to XP. it might not be compatible with vista

though it did that one time with me because i had to reinstall it and i plugged the tablet in before i installed the software

If you previously had other tablet drivers installed, it won't work right. You have to make sure you uninstall any current drivers, then install the new ones.