This occurs when your X installation is missing some fonts.
In unix/x11u.c you will see that we load fonts *helvetica-...* .
if ( Min ( dw->x_len , 1.27*dw->y_len ) < 440 )
nfont = XLoadFont(disp,"*helvetica-medium-r-normal--8*");
else if ( Min ( dw->x_len , 1.27*dw->y_len ) < 600. )
nfont = XLoadFont(disp,"*helvetica-bold-r-normal--10*");
else if ( Min ( dw->x_len , 1.27*dw->y_len ) < 760. )
nfont = XLoadFont(disp,"*helvetica-bold-r-normal--12*");
else if ( Min ( dw->x_len , 1.27*dw->y_len ) < 920. )
nfont = XLoadFont(disp,"*helvetica-bold-r-normal--14*");
else if ( Min ( dw->x_len , 1.27*dw->y_len ) < 1080. )
nfont = XLoadFont(disp,"*helvetica-bold-r-normal--18*");
else
nfont = XLoadFont(disp,"*helvetica-bold-r-normal--20*");
You have two options:
(1) install these fonts on your system; should be easy.
(2) change the fonts requested in unix/x11u.c. To see what you already have loaded, type 'xlsfonts' at the command prompt. From this list pick a fixed width font that has the appropriate font sizes.