Wild strawberry plant that grows... blueberries?

[GardenArtist]

I'm afraid I don't have any pictures, but I believe a description will be sufficient to determine what sort of plant this is.

We live in the NE United States, and we have wild strawberries in abundance here. However, recently we discovered what looks like an invasive vine/ground covering of strawberry plants. The leaves, the flowers... they all look *exactly* like wild strawberries, but at this time of year they get fruit on them that looks like blueberries - exactly like blueberries. We've looked up this information on the web, but can't find anything to tell us what it is, and the curiosity is driving us crazy! Does anyone have any idea of what this plant might be?