I went through exactly the same thing at school, and honestly it was so ridiculous, looking back it makes me laugh.
With me, it was one friend who'd recently been dumped just stirring up a lot of unecessary bitching and everyone else went along with it.
I know exactly how you feel about feeling awkward evening mentioning his name, but its them that have the problem, not you. Jealousy isn't very nice, and nor is a big group of girls bitching- but both always seem to happen!
As everyone else has said, ignore them. I can promise you, they soon tire of it. And its then you realise who you're real friends are.
In my experience, it was the one girl who started it, coming crawling back. But yes honestly, when something else came along, they all soon forgot about it, and until then, try not to worry too much about it, as i said, they're the ones with the problem, not you!