Windows 2003 R2 DHCP server error 1014

Hello to all,
one of domain controller (the master catalog) is running dhcp service without problem. However yesterday I've discovered the following errors:
Event ID: 1014
Source: dhcpserver
Date: 4/2/2010
Time: 4:28:09PM
Description:
The following problem occurred with the Jet database -1022: Jet database read or write operations failed. If the computer or database has just been upgraded, then this message can be safely ignored. If this message appears frequently, either there is not enough disk space to complete the operation or the database or backup database may be corrupt. To correct this problem, either free additional space on your hard disk or restore the database. After you restore the database, ensure that conflict detection is enabled in DHCP server properties. For information about restoring the database, see Help and Support Center. Additional Debug Information: JetBackup.

and

Event ID: 1016
Source: dhcpserver
Date: 4/2/2010
Time: 4:28:09PM
Description:
The DHCP service encountered the following error when backing up the database:
An error occurred while accessing the DHCP database. Look at the
DHCP server event log for more information on this error.

This morning no errors has been found nor dhcp having problem. I can open the DHCP console and see all is running.
I've checked the folder C:\Windows\System32\dhcp\backup and it's present the following folder:
C:\Windows\System32\dhcp\backup\new\ creation date 4/3/2010 7:28AM, which contains a copy of dhcp.mdb, dhcp.pat and two log files.

My question is: the error discovered can be a sporadic jet database error, or may be a corrupted mdb ? Please note that I'm running on the server Symantec SAV 10, could be a sporadic conflit with AV ?
And, in addition to, what is the frequency of backup dhcp database ?

Thanks in advance,
paolo