We have been running into the problem of water leaks under finished walls quite a bit lately. In an apartment building in Waltham, we had this situation in a "garden level apartment". This is an apartment that is mostly below grade.
It was freezing out and they said the water was coming from below the finished wall. This didn't make too much sense. When we got there, the only way we could see what was going on was by opening up the finished wall a little bit.
We opened up the wall underneath the window. There was an ice dam on the window above which was melting. The water was running down the sides of the window, inside the wall, and coming out underneath the finished basement wall.
Naturally, people see water and they think it is coming from the basement, but in this case it was coming from an ice dam above the window. So, a great tip is to keep ice dams off of those windows!
For more information, contact A1 Foundation Crack Repair.