Check the settings in your program?
I know with MS5 that you can get 'tails' only when you use certain brushes.

Maybe you changed some settings or something on accident

Hmmm, this is the default mode I have. I just installed this.

What program are you using?

SAI.

i think your pen nib is starting to "run out"? try pressing your pen nib with your finger, if it sinks deeper than it should, maybe you should try getting a new pen nib and replace it.

Actually I just bought this and installed it this afternoon.

Probably should lower the brush sensitivity, if it's still detecting the stroke long after you've finished drawing the line then the sensitivity is too high.

You could also change the line thickness so it never gets that thin, you know Max Diameter, and Min Diameter. Other than that I can't think of much else other than ending your lines sooner...

us Intuos users get these issues. i believe youtube has some guides on this

To make it easier, what is the term of that twirly end of stroke, again?

i have no idea

Try changing the Min Size in the brush setting (For SAI )

You might have windows ink on. Check the update for the program, and in the tablet settings somewhere there should be a checkbox that says "use windows ink." Turn that shit OFF. It messes with everything.

As for any other reason why you're getting those soft brushlike strokes, you could have the sensitivity turned up to maximum, meaning that the smallest amount of pressure against the tablet causes it to start writing. I know that wacom products and the image editor called GIMP really don't get along.

Download a demo of Autodesk Sketchbook and see if there's any difference in that program when you draw. If you start up autodesk sketchbook and it immediately draws DARK BLACK, then that means windows ink is on.

Hope this helps.