In addition to what Mary suggested, you probably are using one of the screensavers that has little advertisements floating by. Make sure the first button you press on your remote isn't Play or OK or you'll get whatever is being advertised installed. I don't know, but it may also start playing a movie from that advertisement as well. Get in the habit of pressing Home or one of the arrow buttons when you first pick up your remote.
Or, switch to a screensaver that doesn't contain advertisements.
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