I'm not sure why you would be getting this error if it was working correctly before. The file referenced is usually found in the kfm folder inside of includes > pear. I'm including a copy of it here for you in case you can't find it. You should check to see if it is in the following location:
If it is not then you should add it here. If you can find it here then you may need to copy this file to the same location as the file:
Let us know how it works for you.