Yes, but in the range 0..0.1e-19 it works ok...

> plots[odeplot] (F, [t, D(x)(t)], 0..0.1e-19);

ps: the actuall results are still wired...

Thanks for your reply!

I've noticed this dependence too. I am confused with this part:

"further right of .12961725e-8"

Right means bigger for me (as on the real numbers axis). Does this mean that the function has singularity with all the arguments equal or bigger than .12961725e-8?  But why than the error message differ...