Issue with mountain lion

I upgraded from leopard to mountain lion ( 10.8.2) on my iMac ( 2009 4gb/3GHz) just so I could download iMovie 11. Since then I keep having a lock up problem where if I try to move my cursor to the top right and change volume, try to use the search bar ( not sure this is what it is called but the icon to search/locate information ) , the clock doesn't change time. In other words everything is frozen and a beach ball is all that I see. I can use the left side of the screen just not the right upper portion. If I restart my computer all is fine for a while then later it locks up again. Also the computer in general is a little slower than it was with leopard especially after being idle for a while-seems to need extra time to respond when I start again. From reading the forum a reinstall maybe needed but I was hoping for something easier. Any help would be appreciated.

Try OnyX and see if that helps. If not then a clean install is the best thing to do.
Download OnyX for Mac - Maintenance and optimization tool. MacUpdate.com

And you could not go legally from Leopard to Mountain Lion. Need Snow Leopard OS X.6.8 installed in order to access the App Store and purchase Mountain Lion. Not copied illegally or such?

Thanks docx. So far so good. Seems this worked. I used to use something like this-I think it was macsweep-but it didn't work with the new Mt Lion.
Now I am not sure why Harry had to make this little remark which I found offensive and totally unnecessary. Just to set the record straight I did all in a proper manner. I spent my money and went from leopard to snow leopard to lion I just saw no reason to go into more detail in my question. But since you brought this legal issue up - I was doing things the proper way-and as anyone knows who has a computer this is a never ending money pit-just ask Adobe who keeps me chasing photoshop down the money hole. Apple does the same. For a company that has more money than most countries I ended up having to pay-legally harryb2448-for an upgrade Word since my other version didn't work with lion. I had the same issue with my Epson 3170 scanner which lion also doesn't recognize. This too has cost money and time to resolve. I could go on but nowhere did I find any information from apple that I would be having all these issues when I upgraded all because I wanted to have i-movie 11 BECAUSE Apple in its wisdom changed iMovie audio in iMovie 6 . By the way I had gone to another version of iMovie when I bought a new Apple computer -all done legally harrb2448- and found the new iMovie 8 didn't have the audio I liked. As you can see harry you touched a real sore spot with me. I have always done this by the book but feel way too often Apple despite all the great products they have have tested my good nature not to mention my pocket book!

In Harry's defense when you left out SL it was a reasonable conclusion .
In order to get to the bottom of things all the details are needed and would have gotten you a better response.
I find that Apple's upgrades are still a lot lower in cost than the competition and nobody wants to write apps or OS's for free. Have you checked Microsoft's pricing on their OS and Office lately?
Some of the major reasons for having to renew or upgrade would be everyone is moving to 64bit and while certain things 32bit will work on a 64 not all will nor is the developer in some cases willing to write code for both.

Thanks osxx but no worries. One can only respond to information as supplied even if not quite correct.