Hi Dave,

You need to shoot in manual mode.

By selecting anything with automatic exposure, the camera is metering for
the ambient light - and hence goes for a very low shutter speed (which also
explains the blur).

Try starting at 1/250 @ F5.6 and go down from there - ignore the light
meter - just go on how the image looks.

Don't go above 1/250 - at faster speeds the shutter isn't completely open
all at the same time - and you'll cut off part of your image.

Cheers,

Colin

<snip of nonpertinent information>

Put your camera in manual.  Program is not appropriate for working with
strobes, since the camera meters for ambient light.  So you are getting a
setting of 1.6 seconds for the room light, and adding the strobe's light
over that.  Get a flash meter, meter the light from the strobe, and set the
camera, manually.
The only other option is to dink with it, checking your LCD after every
shot, until you get the exposure right.

1.6 sec is way too slow,  you are getting too much ambient light in the
exposure, causing blurring at such a slow shutter speed.

Whenever you are using studio strobes,   shoot with the camera set to M,
which is the manual mode.  Always shoot in manual mode for studio shooting.
In a studio, the camera's meter is of no use.   You need a flash meter, or
just eyeball the histogram on you camera's LCD.

manually adjust the aperture until the image looks good.  Set ISO to 100.
I would set the shutter to 1/125,  or whatever X sync is,  on a 20D , I
think it is 1/250,  but in a studio,  I usually use 1/125.  Shutterspeed
won't matter too much,  unless the shutter speed is so slow it lets in too
much ambient light.  I would adjust the strobe output so that the aperture
is at  f/5.6 or F/8, but any apeture above f/5.6 would be okay,  unless you
really want a narrow depth of field which will happen at wider than F/5.6.
You can move the strobe back,  to nuance the f/stop, if needed,  but having
the the umbrella close as possible to the subject is more desirable

Patrick