Communications is essentially about sending and receiving messages. Communications issues are risks which have happened and may not necessarily be related to conflict. For example, if I'm running tight on budget as the project manager, and I leave a message for a supervisor indicating overtime needs to be curtailed, and the supervisor does not receive the message for two days due to vacation time, I now may have the issue that my project is two days over budget due to a communication issue.
Just yesterday, I had a co-worker email me to print and bring a map -- we were to meet at point A and travel together to point B. The only problem was this individual emailed me AFTER I left home to travel to point A -- no way I could have received that message until I arrived and either started up my laptop, met my co-worker, or consulted my personal communications device. There was a risk that I would have missed the communication and it certainly became an issue. Fortunately, proactive project manager that I am, I printed the directions two days before and had them in my briefcase. My PDA also has access to Google Maps. A double mitigation strategy was already in place!