collision problem

in my ski gaming i have character.the character moves along the terrain.

in the character i have added character control .There is script added to the character for movement in ice(first person walker script).

there is a terrain with resolution width 50000 and length 10000.

when character moves through the terrain side ways small hills are there.but when the character hit the hill no collision happens and he starts to penetrate through the hills and falls down.

i tried a lots of ways not able to solve the problem. here is the link where the character controller values http://img163.imageshack.us/i/screenshotyv.png/

when i place cube in front of the character the collision is happening.but when i place the same cube in side ways the character is just penetrating the cube and penetrating through the hill in side ways and falls.