Why Is My Manager Suddenly Hostile Toward Me? Here's Why

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Dear Liz,
I had my one-year anniversary at work in March.
My manager "Chris" and I had a two-hour lunch to talk about my first year results.
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Chris was very complementary and told me that hiring me was one of the best decisions he's ever made.
After that lunch, Chris sent me a long email message telling me how pleased he was with my first year's performance.
That night I went home and told my boyfriend "Chris is the best boss I've ever had."
Boy, how things have changed since March!
That was only four months ago, but Chris's attitude toward me has changed dramatically. You would never know he used to talk with me one-on-one for hours, sharing his ideas with me and listening to my ideas. Now it seems like he can't stand the sight of me.
The shift started soon after my performance review in March.
First, Chris savaged a report I wrote. He wrote in red ink all over it and scribbled the word "Wrong!" in all caps across a page of graphs I created. The weird thing is that I had shown Chris the exact same graphs before and he said they would make a good addition to the report.
I tried to get a one-on-one meeting with Chris to go over his comments and correct whatever he didn't like about the report, but he kept putting off that meeting. Finally his admin Julia sent me an email message and said "You don't need to meet with Chris about the report. He's going to make corrections to it himself."
I went to Julia privately and asked her why Chris is avoiding me, and why he's been so hostile lately. She shrugged her shoulders and said "Don't worry about it, he blows hot and cold sometimes" but I'm not reassured at all. I've never seen Chris turn on anybody else the way he's turned on me.
Should I talk to HR about it? Should I hope things blow over? I love my job, apart from this issue. I haven't had a real conversation with Chris since early April. He ignores my email messages, ignores me in meetings and looks right through me when I see him in the hallway. What should I do?
Thanks,
Naomi