Odd Mixing Latency setting behavior on Win7 x64

My Win7 x64 laptop uses an IDT HD Audio card. My Sonar Audio settings are Bit Depth 24 and Sample Rate 48000. The sound card will only work at 198 @ 9504. Any other setting will produce clicks and pops.
 
 
However, if I select 198 ms @ 9504 samples and hit Apply. It comes back with 195 @ 9360. Hit Apply again and it comes back with 193 @ 9264. Hit Apply repeatedly and it cycles lower and lower. It will not stay where I want it. So to maintain the desired setting I have to set it one notch above what I want and hit Apply and then never never hit Apply or OK again.
 
Should this be happening? My WinXP x32 desktop w/SoundBlaster does not behave this way.
 
On a side note I see the Buffer size on x64 systems is nearly double what it is on x32 systems.