Fit function ill-conditioned

Matlab fit function throws the following error:

Warning: Equation is badly conditioned. Remove repeated data points or try centering and scaling.

> In curvefit.attention.Warning/throw (line 30)

In fit>iLinearFit (line 672)

In fit>iFit (line 383)

In fit (line 108)

My data: x,t and f(x,t)

I am trying to fit a 2nd degree polynomial through the data

The problem is: The x,t, and f(x,t) values are very similiar

I have also scaled and centered the x and t values to vary from -1 to 1, but I still have this error

Any suggestions?