My object has a lot of textures 512*512, in all explorers (Deep Expl. for example) it views with textures, but #$%^@ when I load it into DBP a half of textures suddenly disappears

.
I tryed to compress textures into 256*256 but doesn't brings the effect.
However I notice that if I loading not all object, but only one of its part there will be no this damned tex. disappering. Why? And also I can load the same part of object again and again, and all textures'll be on there place.
P.S.
I have GeForce4MX 64Mb and 128Mb RIMM