YAHOT: How is this water getting in my basement?

[Squisher]

I would do some deconstruction (drywall and framing) along with fixing some of the likely sources that some have mentioned, however if you do this and fail to find the source you can have pictures taken with an infrared camera that will pinpoint the migration of the water. Price is around $150 for the whole house and this is also a great way to find any sources for heating and cooling issues too around the house.