Bluetooth suddenly stops working

Hi ! 

I have a dell studio 1558 laptop and it's got this Bluetooth problem. I use BT to connect to Internet through my phone as a modem. But sometimes it suddenly stops working and the BT icon vanishes from the taskbar. Every attempt to restart it by Wireless switch, or by restarting BT service/process fails. (this does not happen with WiFi, or any other connection though). The only way I get back Bluetooth ON again is if I put the system to sleep, or I shut down and Turn On (Hibernate, Restart, Log off doesn't work). And this happens more frequently while multitasking than normal use.

I am using Windows 7 Home premium (service pack 0).I have the latest Bluetooth module installed, latest system BIOS installed as available in the dell website. Is this software problem or hardware problem?

What should I do. Please help.......