why has my iMac slowed after updating to snow leopard?

I am an advanced user and I have also the problem of a slow mac in certain moments (Rainbow wheel). As I could see in the Logs:

This message appears several hundred times per day in the system log. Could this be the problem?

I didn't found any hint via Google and Apple.

Any help would be greatly appreciated also from my side. Thanks.

You should start your own topic for this. It really doesn't belong here.

Ursula, slowdowns can be caused by any number of things. First, how much RAM, a k a memory, do you have installed? Snow Leopard may be hungrier for RAM than Leopard was.

Open Activity Monitor in Utilities and post a screenshot (Cmd-Shift-4 and use the camera icon above) of the bottom only of the system memory tab. Like this

Have you updated to 10.6.8?

http://support.apple.com/kb/DL1399

There are other things to look at, but let's start with that.

OK, I think the problem is you don't have enough RAM. Even though you meet the minimum for Snow, which is 1GB, that's really bare bones. What happens when you don't have enough is paging occurs (Page outs in your screenshot.) Since there isn't enough physical RAM, the system starts writing the memory outside to the hard drive, and this is very inefficient and slow. If it keeps up, the computer will just eventually freeze.

Right now you have only 65MB free, and although you have more in "Inactive," which is supposed to be available on demand, it often doesn't work the way it should.

The temporary fix for that is to keep fewer applications open concurrently. The real fix is to install more RAM. If you're in the US or Canada, an excellent place to get reasonably priced, good Mac compatible RAM is from OWC, macsales.com. They also ship internationally, but don't know how costly that makes it.

I would install the maximum for your model. If you call OWC, they can walk you through this and there are videos on their site showing how.

Phone 800.275.4576