level shifter with cmos input creating problem

Hi All,

I am using a level shifter ST2378E. I want to shift 3.3V to 2.5V.
when i apply a
3.3V, 1KHz CMOS Square signal to I/OVcc(3.3V side) and see the output at I/OVL(2.5V side) i see a signal which goes to 2.5V with out noise and the 0V very noisy and noise going upto 2.5V
when i apply 3.3V -- output is 2.5V
when i apply 0 -- output is zero clean with out noise.
when i check all pins with out any input -- 3.3V pins pulled to 3.3V and 2.5V pins pulled to 2.5V.
3V CMOS 1KHz signal at input and see the input in CRO the 0 to 3V signal is shifted to 1V to 3V signal at the input -- and out put is 1 to 2.5V. since the gnd level is at 1V the signal is not completely grounded and looks very noise at 1V level due to transit.
can anybody please let me know why is this happening?
i am applying cmos signal from the CRO test signal through a berg stick

thanks in advance.

Can you post a schematic, and some waveforms demonstrating what you describe?