On of the drawbacks of google maps infowindows is that map will move to make room for the infowindow to display. ebubble( http://econym.org.uk/gmap/ebubble.html) overcomes t
Depending on your needs (which aren't totally clear from your description), you might consider MapTooltip, which lets you put arbitrary HTML into a tooltip. I haven't used it, but it's mentioned in this excellent presentation on Google Maps.
Alternatively, you might be able to make the InfoWindow do what you want with some event handling code. movestart and the InfoWindow's onOpenFn might let you do this - try catching movestart and remembering the map's position, then in your onOpenFn restore the position. This might look ugly, though.