I think that kinda thing only happens with the paintbrush tool. I've used the pencil tool recently and absolutely nothing changes once I finish drawing a line.

I'd just like to interject for a second to point out that Mac isn't an acronym, it's a noun. An all capitalized MAC refers to other things

Yeah I have an imac and it just smoothes it a bit at 0 smoothing as well. Other than that it stays at the same place where I drew it.

Could you illustrate your problem in a video?

Antialising gets added to every stroke after it's been drawn in flash, which is why it could appear to jolt. However if serious repositioning of your stroke changes then a larger problem occurs. My advice is to check in two other programs and see if you have any jolting after the line has been drawn. One being Photoshop testing bitmap/raster. Which creates real time antialising so you should be able to see if this is a flash isolated incident. The other is ToonBoom Studio, which has the same vector engine as flash, however unless told (in the GL properties), will not show antialising until you preview your animation (ctrl + enter), or export your animation to swf.

This way we can see if it's hardware or software related. If its hardware, you may have a conflicting driver, but I doubt it is from what you said.

Xero, it doesnt matter if you use mouse or tablet, the problem is still there. and yes stone, this happens for me too. It always has. I think it has something to do with, like Satera said above, the anti-aliasing...thus why it still happens even if you have smoothing set to 0. I've only animated on a pc with windows as well. I'm curious to see how much different flash would seem on a mac.