I went on a bit of a twitter rant recently.
@SysAdm1138 What if you're the employee on the other side of the desk? There's only so many times you can ask for a decision...-- Kevin Elliott (@KevinCElliott) October 20, 2014
Good question, since that's a very different problem than the one I was ranting about. How do you deal with that?
I hate to break it to you, but if you're in the position where your manager is actively avoiding you it's all on you to fix it. There are cases where it isn't up to you, such as if there are a lot of people being avoided and it's affecting the manager's work-performance, but that's a systemic problem. No, for this case I'm talking about you are being avoided, and not your fellow direct-reports. It's personal, not systemic.
No, it's not fair. But you still have to deal with it.
You have a question to ask yourself:
Do I want to change myself to keep the job, or do I want to change my manager by getting a new job?
Because this shunning activity is done by managers who would really rather fire your ass, but can't or won't for some reason. Perhaps they don't have firing authority. Perhaps the paperwork is too much to bother with firing someone. Perhaps they're the conflict-avoidant type and pretending you don't exist is preferable to making you Very Angry by firing them.
You've been non-verbally invited to Go Away. You get to decide if that's what you want to do.
Start job-hunting, and good riddance. They may even overlook job-hunt activities on the job, but don't push it.
Staying and Escalating
They can't/won't get rid of you, but you're still there. It's quite tempting to stick around and intimidate your way into their presence and force them to react. They're avoiding you for a reason, so hit those buttons harder. This is not the adult way to respond to the situation, but they started it.
I shouldn't have to say that, but this makes for a toxic work environment for everyone else so... don't do that.
Staying and Reforming
Perhaps the job itself is otherwise awesome-sauce, or maybe getting another job will involve moving and you're not ready for that. Time to change yourself.
Step 1: Figure out why the manager is hiding from you.
Step 2: Stop doing that.
Step 3: See if your peace-offering is accepted.
Figure out why they're hiding
This is key to the whole thing. Maybe they see you as too aggressive. Maybe you keep saying no and they hate that. Maybe you never give an unqualified answer and they want definites. Maybe you always say, 'that will never work,' to anything put before you. Maybe you talk politics in the office and they don't agree with you. Maybe you don't go paintballing on weekends. Whatever it is...
Stop doing that.
It's not always easy to know why someone is avoiding you. That whole avoidant thing makes it hard. Sometimes you can get intelligence from coworkers about what the manager has been saying when you're not around or what happens when your name comes up. Ask around, at least it'll show you're aware of the problem.
And then... stop doing whatever it is. Calm down. Say yes more often. Start qualifying answers only in your head instead of out loud. Say, "I'll see what I can do" instead of "that'll never work." Stop talking politics in the office. Go paintballing on weekends. Whatever it is, start establishing a new set of behaviors.
Maybe they'll notice and warm up. It'll be hard, but you probably need the practice to change your habits.
See if your peace-offering is accepted
After your new leaf is turned over, it might pay off to draw their attention to it. This step definitely depends on the manager and the source of the problem, but demonstrating a new way of behaving before saying you've been behaving better can be the key to get back into the communications stream. It also hangs a hat on the fact that you noticed you were in bad graces and took effort to change.
What if it's not accepted?
Then learn to live in Siberia and work through proxies, or lump it and get another job.