I'm so sorry to hear that your wife painted that picture of you to another man...that's just wrong! And yes, in my book even online affairs are affairs....it's a way for her to escape your marriage without actually leaving.
Ok, here's my next question. Have you had "the talk" with her. You know the one about the problems in your marriage, what needs of yours aren't being met, and what the consequences will be if things don't improve? I know it's a tough talk to have, and I know you have a S to think of as well...but have you done that?
Also, you didn't mention how long you two saw a C. How much time did you give it? FYI, it's taken my H 7-mo to really start making progress...primarily because I think it's taken him that long to really start being honest and let down some defenses.
There's definitely something going on w/your W...what's her schedule like? Can you be certain she's not having an A?