well...i don't know if anyone else has had this problem...but in 1.3 build 3 i was playing on quarry, and well...i was fall hovering from sky and hit the wall...well it didn't stop me, i went straight through the wall...i will try to do it again sometime and try to figue out at what angle i did this, but it was weird...that has never happened to me before in bz2...(well in buildings yes...but not the actual mounds of dirt...
did you pop out the other side or did the viewpoint just go thru the dirt?
If you went all the way thru then this might be caused by a corruption in the BZN file
if it was just the camera going underground then this is normal, since there is about a 1-2 foot culling radius around the veiwpoint itself, which is why some objects disappear into your face when your going fast enough (like the ground)