weird smell from A/c

Just recently my autobot has this odd smell that comes out of the a/c ducts. Kind of strange to explain. Or as my best friend/brother puts it, " it smells like an old dirty twat"

It usually happens when i have the car off or not use the a/c a day or 2, and it is usually quick, doesn't last long. Rarely do i get it sporadically, but it's strange. Has anyone ever had that same problem before? ( be any aveo or model?) If so, how do you get rid of it?

Also, where is the air filter for the cabin?

thanks

Talk about a done to death topic...
http://www.aveoforum.com/forum/googl...=1234j232518j9