The same thing happened to me.
1. You will need to know the location of your iTunes library for later, the default is under music under your username. If its not there find it and remember where it is for later.
2. Then you have to exit iTunes and create a new empty library. To do this hold the option key when you open iTunes. Choose create Library on the pop up dialogue. Create the library anywhere on your system, you can delete the entire library once you have completed your iCloud changes.
3. When the library opens in iTunes it will be empty. Click on iTunes Match and click the start button. after it finishes all of the songs on your iCloud match account will be listed under music.
4. you can select up to 1000 at a time and delete them.
5. when you have deleted everything close iTunes and open again holding the option key and navigate to your original library, usually in the music folder under your username. You should be all set and can click iTunes match again and your account will be populated with the ones in your current library.
6. You can navigate to the temp library you created in finder and delete it as it is no longer needed.
Good luck, I hope this helps.
I have tried this solution numerous times. When I set up iTunes Match with a blank library, it says there are 0 songs available in iCloud. All of my devices (iPad, iPhone, and AppleTV) show there are no songs in my cloud, but all the songs in my library have a status of "Exceeded Limit." This is so frustrating.