Two Q's: Servo Hum and FreqMod issues

Got to questions for you wise folks here in CCED...

#1 - I've got my servos working well on the bench. My maximum
velocity is set to .60 ips, which should be within the range of my
servo motors. When I jog, say by running a "G0 X10", the motors
accelerate on a nice conversevative acceleration profile. When they
reach their max velocity they start to ruble/hum.

So Q#1: is this normal?

I assume this is normal because the servo drive is doing is feedback
loop thing, and breaking the motor to prevent it from going too
fast. Even though I've already tuned my motors using the gecko
osciloscope method, I want to be sure that this isn't a symptom of
being out of 'calibration'.

#2 - I'm using steppermod right now, and all works perfect. When I
switch to FreqMod with a period of .000025 (150mhz pc) and
STEPPING_TYPE=0 (drn, step), funny things happen. When I run a
command like "g0 x5", the motor seeks to about where 5" would be,
but then the motor reverses and slowly seeks backwards and doesn't
stop.

So Q#2 - any ideas why freqmod is behaving badly.

Thanks to all. Have a great weekend.
Jake