I cannot determine the exact orgin of the data... Google maps show our location correctly, but Foursquare is using a mapping system that yields incorrect results... BAAAAD for business, with no intuitive way to correct the problem!
I don't do much with Foursquare, but I've had this same problem with other mapping services and I know it can be a pain to resolve. Foursquare may only use Twitter for their support, but they are pretty quick about getting back to you. For kicks I summarized the problem you are having in a tweet like this:
If you have my business address correct but it is showing wrong on the map, how do I correct this?
Within a few minutes, they replied:
No worries. Send us the URL to your Foursquare listing and we'll take care of it. Thanks for your cooperation!
Sounds like you just need to tweet them the address and let them know it's wrong and they'll update it for you.