Nathan, often center channels are placement sensitive. Do you have the speaker in an entertainment center? If so, try pulling out so it's flush with the edge, or even past it a bit.

Besides that, some movies are just mixed poorly--meaning the dialogue will sound kinda bad regardless of speaker issues.

Also, try to get the speaker pointed at you. What center are you using?

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose