Hi, Edwin, ignore the message.
This is, in my opinion, a flaw in the design of OneCare. Defrag during Tune-up will run for a limited period of time and does not check the status of the file system before running. If it runs out of time, you'll see that message in the Tune-up report. You may be able to eliminate this by doing a manual Defrag shortly before Tune-up is going to run, but even that might not help. However, the Defragmentation performed during Tune-up *is* successful in that fragmented files were optimized while it ran, so a percentage of your disk is not fragmented when Tune-up completes. The nature of the file system is such that it will immediately begin fragmenting again, though, so a perfect completion in Tune-up doesn't mean that you will see significant reduction in fragmentation and/or increase in disk performance. Every little bit helps, though, so OneCare is helping. Simply ignore the message for now and know that the defragmentation that took place worked.
-steve