I'm a man and if I had to name my ten closest friends, eight of them would be female. My best friend is female. We're very close, and people have often made an assumption, but nothing has ever happened nor will it. We are like brother and sister (possibly because we are both only children). We're currently both single and went on holiday together. Same hotel room (twin beds).
My ex-partner of 9 years was introduced to my female friends very early on, so she knew the score. However, a few years down the road, she started making derogatory comments. When one of my female friends split up with her bloke, my ex came out with "well, you two can get together now; you get on so well and she's so attractive". She said it was a joke, but it clearly wasn't. She had a particular problem with my best friend. I made every effort, my friend made every effort, but she caused an awful amount of friction.
I spent less time with my friend and rarely saw her unless it was in a group situation. She felt pushed aside, which was unfair, as she'd done nothing wrong and had done everything she could to be friends with my partner. My partner started to accuse me of going behind her back to meet my friend (which was not the case).
She couldn't handle it and it really impacted on our relationship to the point where I felt untrusted. She then declared that I had to choose her or my friend. I chose my friend. I'd known her longer, we'd been there for each other in some really appalling times (my first girlfriend was killed in a car crash).
My ex declared to everyone, all our mutual friends, that this proved there was something going on and we'd be a couple within 3 months. Three years later and still nothing has happened between us. It won't. It's not like that. I've never crossed a line with any of my female friends.
Men and women can be friends. In my experience men seem to have less of an issue of a woman having male friends than vice versa. I also think it's often generational - it's much more common now for mixed-sex friendships. But I do think if there has been a romantic/sexual history, it can be very awkward and unfair on a new partner.