The Belkin adapter is a Broadcom bluetooth adapter (just rebranded):
http://www.amazon.com/Belkin-F8T016-Bluetooth-Laptop-Adapter/dp/B001E96JBK
http://www.belkin.com/uk/support-article?rnId=2561
Likewise the Dell Wireless 365 is a Broadcom adapter.
Its possible the drivers are sharing some common components. Try the Broadcom Bluetooth Update: