[CentOS] Software RAID-1 partition constantly syncing

I have a partition set up as software RAID-1 on a CentOS 5.3 machine. 
Today, the system was rebooted, when it came back up I noticed that it 
had started to resync. It completes the sync, then immediately starts again.

 From the log:
Jul 29 09:46:02 cbserver kernel: md: syncing RAID array md2
Jul 29 09:46:02 cbserver kernel: md: minimum _guaranteed_ reconstruction 
speed: 5000 KB/sec/disc.
Jul 29 09:46:02 cbserver kernel: md: using maximum available idle IO 
bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jul 29 09:46:02 cbserver kernel: md: using 128k window, over a total of 
239946752 blocks.
Jul 29 11:02:01 cbserver kernel: md: md2: sync done.
Jul 29 11:02:01 cbserver kernel: md: syncing RAID array md2
Jul 29 11:02:01 cbserver kernel: md: minimum _guaranteed_ reconstruction 
speed: 5000 KB/sec/disc.
Jul 29 11:02:01 cbserver kernel: md: using maximum available idle IO 
bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jul 29 11:02:01 cbserver kernel: md: using 128k window, over a total of 
239946752 blocks.
Jul 29 11:56:36 cbserver kernel: md: md2: sync done.
Jul 29 11:56:37 cbserver kernel: md: syncing RAID array md2
Jul 29 11:56:37 cbserver kernel: md: minimum _guaranteed_ reconstruction 
speed: 5000 KB/sec/disc.
Jul 29 11:56:37 cbserver kernel: md: using maximum available idle IO 
bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jul 29 11:56:37 cbserver kernel: md: using 128k window, over a total of 
239946752 blocks.

Any idea what is causing this? And how to make it stop?

Thanks!