These are some of the possible remedies that you can take/check for.

1. Check for any kind of cron job scripts that would do a backup of the control file simultaniously.

2. Check for any scripts that would modify the file permissions temprorily

3. IF the above two had been ruled out, then try to enforce the serialization on the disk read by changing the following parameter

disk_asynch_io = false; ( This should fix the problem for you)

Changing this parameter in your initSID.ora requires a bounce of the instance.

Good luck,
Sam