I had to debug an old project in 2004 so got one old 2004 machine but I was not able to get my visual studio to attach to the Biztalk service . The machine had .net 2.0 Framework installed .
Some googling and saw this post from Tom about problems with BAS installation and whidbey.
So on similar lines I made the followwing changes to my BTSNTSvc.exe.config
<?xml version="1.0" ?>
and now you can attach your debugger , go ahead and debug !