help with equation

[t t]

Hi, everyone!
Thank you for your attention.
I got to solve numerically higly non-linear equation and get the following error.
I use Octave 3.6.3 and lsode seemingly is the only included ode.
Best wishes, lan

function xdot = f (x, t);
ep=0.000001;
si=-1;
a=2;
C=100;
xdot = [x(2), -ep/si*(-a*x(1)^(a-1)+C+2*si/t*tanh(x(2)/ep))*cosh(x(2)/ep)^2]';
endfunction
x0 = [100; 1]';
t = linspace(1, 12, 10000)';
lsode_options ("integration method", "stiff")
x = lsode ("f", x0, t);
plot(x(:,1), t);
print -deps R.ep

LSODE-- WARNING..INTERNAL T (=R1) AND H (=R2) ARE
SUCH THAT IN THE MACHINE, T + H = T ON THE NEXT STEP
(H = STEP SIZE). SOLVER WILL CONTINUE ANYWAY
In above, R1 = 0.1000000000000D+01 R2 = 0.0000000000000D+00
LSODE-- AT T (=R1) AND STEP SIZE H (=R2), THE
CORRECTOR CONVERGENCE FAILED REPEATEDLY
OR WITH ABS(H) = HMIN
In above, R1 = 0.1000000000000D+01 R2 = 0.0000000000000D+00
error: lsode: repeated convergence failures (t = 1; perhaps bad Jacobian supplied or wrong choice of integration method or tolerances)
error: called from: