WS2801 Questions?

Hi everyone, i am a lurker in this forums, normally sort my doubts with other people mistakes and accomplishments, but this one is messing with me...

I have bought a WS2801 some RGB leds, and made a circuit according a schematic from adafruit

and been reading the datasheet looking at code and stuff.
but im still not understanding.

So...
step 1: CLK low for more than 500us
step 2: send the 24 bits i need with the 24 clock rising edges.
At the 24 clocks it will change color.
My problem with my tests is that if i send FF FF FF for white color, all on it freaks out not lightning one of the leds.
but if i send FF FF FE it works, so i cant attain the last bit in duty ratio.
Anyone care to explain why?

Thank you very much for your time.

Datasheet copy:
Gray Scale Data Word Format and Timing
CLK pin keeps low more than 500uS will make the WS2801 internal status register reset, and at this moment, the gray scale data in the data shift registers will be latched.
Now WS2801 is ready for gray scale data transport. When the WS2801 receives total 24 clock rising edges, the WS2801 enters relay mode, which relays the input signal got from CKI and SDI with very low distortion (100pS typical) and very low delay time ( 8 ns typical). The data format and the timing diagram can be seen in Fig 11.
The gray scale data frame is comprised of 3 gray data words, each data word is composed of 8 gray scale data bits, total 24 bits.
The 8bit gray data can easily realize the linear 256 LED gray levels control.
During data transfer, the first bit is the data frame signal, then is the MSB of the ROUT channel, the last one transferred into the
data shift register is the LSB of the BOUT channel.
Gray scale data 0000 0000 is for the minimum 0 duty ratio, and 1111 1111 is for the maximum 255/256 duty ratio.