This has happened again. This time it's really awkward as this person shares a long workstation with me and sits several feet next to me all day. We got along great, always laughed, joked and chitchat etc. The guy started giving me a "fake polite smile" when I made a comment, as if to say I'm not interested or you are annoying me. He stopped making comments or engaging me in any way. Except for good morning and goodnight. Not wanting to bother him, I ceased engaging him and now sit in silence for 8 hrs. Thank God for headphones! I am getting used to it now close to one month later, but it's still quite depressing to me since there is no explanation for this. Even a nearby coworker noticed we don't talk anymore. To me this is more unnerving because I have to sit next to this person 40 hours a week.