I can't use the minimun size, when I try too it looks like a 3*3 brush (when I enable JTablet) and I can't trace from the pointer (it traces like 2 or 3 pixels below it). When I don't actcivate JTablet, I can use the brush with one pixel but only when doing straight lines, otherwise the flow is interrumpted. Any idea of what's happening? I already reinstalled JTablet and my tablet.

Dunno.. there's a few bugs lately.. I'm happy when I can just open the place

what type of brush are you using (from the 4 on the left)? what zoom (yes, this affects brush selection)? are you using an angled brush? are you using fractional brush sizes?
what do you mean by 'minimum size' ? (the minimum brush size now is something like 0.001 pixels, so I assume that's not what you mean)

any brush, Any zoom, it is not angled. I use the first one of the 6 at the top. without anti-alias or bending. :C It's not my tablet, I just tried it with the mouse.

ok. try changing your brush type after selecting that brush. pick one of the bottom 3 of the 4 on the left. it's probably a bug with the new fractional brush support when used without antialiasing which I don't really have time to fix right now. the fact that most people haven't commented on this particular problem leaves me to believe that most people are using antialias mode (the default). I will look into it when I can.