Sometimes you will encounter something very weird in the ULS logs. The only entries that are logged are “Tracing service lost trace events” log entries. To resolve this issue, just restart your Tracing service. You can do that from the command line using the following commands:

net stop sptrace (to stop the tracing service)
net start sptrace (to start the tracing service)

This will do the trick for you.

In addition, you may want to check out the free SharePoint Troubleshooting issue I recently authored forUnderstanding SharePoint Journal .