ArcMap 10.1: why can't I save directly through Symbol Selector. Always greys out

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I save a lot of line types/hatching/fills as styles. However, my MXD file keeps showing a greyed out box in the Symbol Selector window which is really annoying. I have attached a picture of the window screen. Any idea what I can do? I really don't want to have to go through the Style Manager each time.

Thanks-

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