Not often but it has happened several times to me... I'm in intercourse and loose my erection just like that..
I've mentioned it to a doctor who said (with no deep examination) it was a psychological issue..

I've never been insecure about sex until a long relationship ended badly for me...
Then, very frequently, I would not be able to intercourse with new girlfriends, despite wanting it badly... I would masturbate myself with no problem but would loose my erection right before starting to have sex.. So frustrating. It happened several times and really spoiled, I'm sure, some relationships cause I couldn't cope with it and would feel very bad and just avoid the girlfriend...

I've learned to deal with it by lowering expectations and saying to my girlfriends that it "may eventually happen and it's nothing serious.. Just a nervous issue..." ...

The thing is, it still happens every now and then, although I'm in a stable relation now and very comfortable, with a girlfriend that tells me it has no importance whenever it happens (but I see she is puzzled by it)...
I feel very, very frustrated to the point I would beat the ***** of myself for letting me down...

So, has this happened to any guy around here? How have you dealled with it?
And what about girls... has it happened to your boyfriends? How do you felt about it?

Thanks in advance..