Class meetings are a fantastic way to work on these kinds of issues. I don't want to say 'resolve' because children this age are still learning these skills, so they need to be revisited the same as spelling and math facts. The effectiveness comes from this being their problem and their solution. If it is Your problem and/or Your solution, they don't have as much invested in the outcome.
In my class, either the children can call a meeting, or I do if it is clearly something like what you mentioned that the group clearly has to work on. We pick a good time, then have a discussion. The ground rules are:
1) One person can speak at a time, everyone else listens.
2) Listening means trying to understand the other person's point, even if you don't agree. No one can listen with his/her hand up, nor interrupt.
3) Everyone gets a turn to talk who wants one.
4) Only the issue being discussed is permitted - things that happened last week, last year, etc. are not up for discussion (ie stick to the topic)
5) During brainstorming possible ideas for solutions to the problems, no one can nix them, boo, etc. Ideas are out to consider, not to criticize.
6) The group discusses options and agrees on what steps to take to remedy the situation. I have ultimate veto power in case the solution is not workable, but I have never had to use it.
All of that sounds like a lot of rules, but once they are used to the process, it pretty well happens with very little help from me. The children are committed to working things out, and empowered by the knowledge that they can. They also learn excellent skills that will extend into adulthood.