Masteries: which path for a support champion?

Not a complaint, just genuinely puzzled by the behaviour. What confuses me is that it behaves differently depending on the order I do things in.

Any pointers appreciated, even partial ones.

Only partly related, but give it a clean reinstall before assuming the hardware is at fault.

Good luck, it is a common snag.

Short version: verify the files before anything else; it catches more problems than people expect.