In cases like this, it's usually only one or two objects that have been sent far away, most often because you picked up an object, moved it and set it down without afixing it to a workplane.
Try different views (especially if you've named them) and see which takes up the least amount of space on your screen. From your description, you can see the cluster of objects that are supposed to be close together, so this shouldn't be too difficult.
Once you've determined which view to use, try a Sweep Select of the area that does not include the cluster of objects you want (or Select All and De-Select as Torfinn described). From here, you could zoom into the corners of the selected area to see what's there (you could also bring up the Selection Info palette to see a list) or you could just move these objects much closer to the cluster (the advantage being that you won't have to draw them again).
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