New Maxima user has problem



Yesterday I downloaded and installed Euler/Maxima on my computer (HP dv2500t, Vista Ultimate (x64)).  I skimmed the Maxima help files and learned how to pipe commands to Maxima from Euler.  Then from Euler I gave the commands
 
: f(x):=log(2-cos(x)+sqrt(3+cos(x)*(cos(x)-4))) $ : r(n,p):=(1/%pi)*integrate((1-exp(-abs(n)*f(x))*cos(p*x))/sinh(f(x)),x,0,%pi) $ : r(1,3) ;
expecting to see the reply  46/(3*%pi) - 4  but instead I got the reply, 
   Maxima encountered a Lisp error: 
    Error in PROGN [or a callee]: Bind stack overflow. 
   Automatically continuing.    To reenable the Lisp debugger set *debugger-hook* to nil. 
 
Can anyone tell me if I have done something wrong to produce this result?
 
Thanks,
Bob Baker
 
P.S.  r(n,p) is the resistance between node (0,0) and node (n,p) in an infinite square lattice of 1-ohm resistors.