I have gotten this too when the Forwarder has been setup on a server with a lot of files in the monitored directory. This message indicates that there are more files than the Forwarder can handle at one time. It is not a problem, notice that the message level is set to "INFO". Within time, and this depends upon how many files you have and the number of open files handles are defined for the Forwarder, it will catch up and process all of your logs.
You can get more specific info with the Answer to the question "4.1.2 upgrade TailingProcessor - File descriptor cache is full"
