I'm glad to inform you that changing the Section "Screen" DefaultDepth from 24 to 16 the problem seems to have disappeared: at least I could run my famous test (i.e. gv foo.txt) many times without locking the system :-)
Although I think you could reasonably close the bug, one question remains: I had not set that value to 24 and, if I recall well, when I configured X in old Woody and tried to run it with the wrong value, some 'goblin' would come out from within the X Window System and tell me that depth 24 was not supported by my video card! Regards, Ennio. -- [Perche' usare Win$ozz (dico io) se ..."anche uno sciocco sa farlo. \\?// Fa' qualche cosa di cui non sei capace!" (diceva Henry Miller) ] (°|°) [Why use Win$ozz (I say) if ... "even a fool can do that. )=( Do something you aren't good at!" (as Henry Miller used to say) ]