Really simple DSP high-pass filter question

Good afternoon.  I've worked with DSPs for some time now, but i'm scratching my head at a simple high-pass filter implementation that yields unexpectedly attenuated output.
 
My scenario is simple, i've used the fir1 function in MATLAB to generate 65 coefficients of a LPF.  The freq response shows the passband is 0db, as it should be. 
 
However when i use these coefficients in a HPF application and input a signal that should be well into the passband i get an output that's attenuated by almost 1000.
 
Has anyone else used MATLAB fir1() to generate HPF coefficients, is there a scaling factor or some application detail i've glossed over?
 
-Alexander

I realize that it may have been a typo, but you said, "i've used the fir1 function in MATLAB to generate 65 coefficients of a LPF." Then you said, "However when i use these coefficients in a HPF application..." So you designed a low-pass filter and then used it as a high-pass filter? That might give you the 60 dB of attenuation you're seeing. You can only do this if you apply spectral inversion to the LPF coefficients, which you didn't mention.