Infinite loop in a interpl?

Hi,

While solving an ode with ode45 I use a spline like this:

X_0 = interp1(r(:,1),r(:,2),x,'spline');

However sometimes the spline appears to get into an infinite loop where ode45 will not output any answers and if I cancel the program it always stops while in this line of code, usually in 'spparms'.

spparms at 116

In ==> spline at 90
   spparms('autommd',0);

In ==> interp1 at 280
        yiMat = spline(xCol.',yMat.',xiCol.').';

Any ideas in to what is going wrong? Will the spline function 'interp1' get stuck in a loop if the fit is too bad?