It looks like you may be using an old Twitter Source which is now included standard in the apache flume distribution. You'll need to update your source class to reflect the new location:
If your original source looks like:
TwitterAgent.sources.TwitterSource.type = com.cloudera.flume.source.TwitterSource
Please change it to:
TwitterAgent.sources.TwitterSource.type=org.apache.flume.source.twitter.TwitterSource
