I don't think it's wrong to spend time with the opposite sex so long as the boundaries are clearly established. I had dinner with a female friend the other night and she knew what I was going through and it was just a way to catch up, hang out and feel good about myself with some good compant. I did dress nicely for it because I've always enjoyed dressing up for dinners and the like. So as long as the intentions are clear from the get go, it should be fine. Just my two pennies.
