Bluetooth and Wifi operate on the same frequencies.
The long story is here
Bluetooth and Wireless Ethernet devices operate within the 2.4 GHz band. The difference is that that Bluetooth uses frequency hopping (at 1,600 hops per second) to hop 1mhz at a time over the entire 2.4 GHz band. WiFi (B and G), on the other hand, uses direct sequence and only occupies approximately one third of the 2.4 GHz band. As a result, Bluetooth hops all over WiFi transmissions.
You have confirmed this yourself by seeing the problem go away when you stop using and/or disconnect the laptop's WiFi adapter.
There are multiple other devices that operate on the 2.4ghz spectrum... including the microwave oven that is probably in your kitchen, cordless land-lines, etc. It could even be WiFi signal interference from your phone, if your cell phone also connects to your WiFi router.
Until significant changes are made to how Bluetooth operates, or how WiFi operates, problems like this will continue to happen between the two.