Are they misfires or feeding/ejection issues?
If the gun is chambering and ejecting rounds without issue, but the firing pin is not hitting the rim of the case to set it off you might have other issues.
You say there is 1000 rounds through it? Did you have these issues the whole time or just lately?
Have you tried different ammo?
Have you cleaned the gun thoroughly? Including firing pin, spring, and channel?
You need to give us a little more info.
Edit: Sorry just saw about the 4-5 different brands of ammo. If this is the case then there is something else wrong here, and I would be cleaning the #### out of the firing pin channel, spring, etc. Lightly oil it up, but not heavily. .22's tend to be pretty dirty guns and if your firing pin channel has enough crap built up you can get such a problem.
This was the first problem to happen on my 10/22 after never cleaning it in a couple thousand rounds.