plot3d fatal error in wgnuplot



Some plot3d plots blow up, but some very similar ones have no problem:

plot3d(x*y,[x,0,1],[y,0,1]) =>
  the instruction at xxx referenced memory at  yyy
Unhandled exception in wgnuplot.exe (CRTDLL.DLL): 0xC0000005: Access violation

Same problem with:
plot3d(x,[x,-2,2],[y,-2,2]);
plot3d(x+y,[x,-2,2],[y,-2,2]);
plot3d(x+x*y,[x,-2,2],[y,-2,2]);

On the other hand,

plot3d(signum(x)*abs(x)*y,[x,-2,2],[y,-2,2]); => no problem (values
the same everywhere!)
plot3d(x*y*1.0000000000001,[x,-2,2],[y,-2,2]) => no problem
plot3d(x*y+1.0e-200,[x,-2,2],[y,-2,2]) => no problem
plot3d(x*abs(y),[x,0,1],[y,0,1]) => no problem
plot3d(0,[x,-2,2],[y,-2,2]) => no problem
plot3d(x+y+x*y,[x,-2,2],[y,-2,2]); => no problem

I have Visual Studio installed on my machine, but apparently wgnuplot
doesn't include symbols, so I can't give a stack trace.

What's going on, and how can I get better debugging info?

                 -s

Maxima 5.11.0 GCL 2.6.8 W2k Athlon