Why did my CZ 452 decide to shoot poorly today?

[PowPow]

I've had it about a month. 22 LR.
Put a Leupold 3-9x40 AO on it, using $6.00 tip-off rings from Academy, while waiting on some nice rings.
After trying I smorsgabird of ammo, I settled on Blazers and it would shoot 5 holes touching at 50 yds, almost every time.
Almost 1000 rounds through it.

After a couple of false starts using Millet rings, I got some Burris Signature rings for it last night.
I have mounted dozens of scopes before; can't see any thing that I did wrong here.

Today the thing went nuts; 2-1/2 gourps at 50 yds.

I plan to take the scope off and put it back on.

What else should I do?
Could a dirty barrel make it shoot stupid all of a sudden?
Could a gun be funny about scope rings, like it is about a bedded stock?
Would shooting my 10/22 make it jealous?
What next?

[alan in ga]

It would seem that since a scope/mount change is the only thing you've done, THAT would be 'suspect'.

[PowPow]

Yeah, I was hoping to hear it was "Inaccurate Friday" or something else.

Hate to put those cheap rings back on.  The only apparent difference in them and the nice ones is finish. Same l,w,d.


I'll reposition it and see if that helps before I change back.

[anweis]

This is a new rifle, and it has 1,000 rounds through it. It actually needs cleaning. Mine did the same.
It took 40 rounds to get to 1/2" groups at 50 yards and it shot like that for about 800 rounds, after which the groups opened. I cleaned, and it shoots great again. I am going through cycles of cleaning at about 1000 rounds now. Nothing aggressive, just a patch wrapped around a .17 brush and oil, followed by dry patches. 

[PowPow]

Well, I tried both reseating the scope and cleaning the barrel, and it tightened back up, at least at 20 yards on the basement.
Since I am using Blazers almost exclusively, I will probably clean it every time I open a new brick.
Thanks for the input.