Hi,
For S60 SDK 5th Edition. You can use BT driver with come with SDK under
S60tools\S60Bt. After install the driver you should see Bluetooth for S60 SDK under USB section (Not bluetooth) of...

try this link. There are links point to download STEW
http://www.symbian-guru.com/welcome/2009/02/stew-lets-you-tweet-from-your-nokia-5800-xpressmusic.html

It's work for me as well. Thanks ( I spend 2 days for this problems!)
It's will be helpful if someone can put note in installation guide.
Can't believe swap the path make the different.