I have lots of friends at work who are men, but is because i usually get on better with guys - I treat them pretty much the same way as i treat my female work friends - I don't fancy them, and i am pretty certain that they don't fancy me. We chat about our partners and kids and telly and what we are doing at the weekend, go and get our lunch from the canteen together etc. My husband has worked in an environment that is predominately women, and therefore he chats about the woman at work he is friends with - I am absolutely positive that there is nothing going on.
I also get on better with my husbands best friend than I do with his best friends wife - I don't fancy him at all, I just have more in common with him than I do with his wife.
Having said all that, i met my husband at work, but we both knew straight away that it was more than a friendship.