You could try using a different skin and se if there is a narrower one. There might also be an option to have the player size according to the video so you should check the properties of the FLVPlayback in the help documentation. One other thing in case all else fails, make sure your video is actually the size you think it is and it isn't including tarnsparent areas to the sides.
Most likely you have the video player dimensions set wrong. The video itself will keep it's aspect ratio (width to height) even if one or the other dimensions is not correctly set.... so the video won't look squished down or stretched up and down.
Space on the sides means that the height is not great enough to allow the video to display at it's full width. Space at the top and bottom means that the video is not wide enought to display the full height.
When using the FLVPlayback, if you use a skin with the controls under the video, you have to add the height of the controls to the height of the video.... so for example a 400px x 300px video should be displayed at 400 x 325 or so. You'll have to experiment a little to find the exact height of the controls.
Thanks for your sugestions!
Looks like the problem had something to do with the settings I chose when rendering
my video clip as WMV.
I exported the video from Premiere Pro as Microsoft DV AVI then converted
it FLV in Adobe Media Encoder and the playback component is now the same
width as my video.
Please see screenshot bellow -