CBU - Backup Failed with code 13 (internal error)

I am running Comodo Backup (Version 4.0.1.74)

This error is only occurring on the incremental backups…

 ==============================================================
 Log File contents...
 ==============================================================
 27.02.2012 06:00:05 Running scheduled backup T:\ComodoBackups\
 			IncrementalBackups\backupCF_inc_files|DATE1|.cbu
 27.02.2012 06:00:05 Creating New Backup...
 27.02.2012 06:00:05 Searching specified backup base
 27.02.2012 06:00:06 Base backup found in initial location T:\
 			ComodoBackups\IncrementalBackups\
 			backupCF_inc_files_15_02_2012.cbu.
 27.02.2012 06:00:07 Opening backup file T:\ComodoBackups\
 			IncrementalBackups\backupCF_inc_files_15_02_2012.cbu
 27.02.2012 06:00:07 Determining base cbu information...
 27.02.2012 06:00:07 Base was created Wed 15.Feb.2012 06:00:06
 27.02.2012 06:00:07 Creating incremental backup "T:\ComodoBackups\
 			IncrementalBackups\backupCF_inc_files_27_02_2012.cbu" 
 			(incremental depth 1)
 27.02.2012 06:00:11 Error Occurred while reading parent backup.
 27.02.2012 06:27:26 Email notification sent successfully!
 27.02.2012 06:27:26 Backup failed with code 13 (Internal error).
 ==============================================================

Windows SBS 2003 Standard Edition (fully patched as of 23Feb2012):

 OS Name	Microsoft(R) Windows(R) Server 2003 for Small Business Server
 Version	5.2.3790 Service Pack 2 Build 3790
 Other OS Description 	Not Available
 OS Manufacturer	Microsoft Corporation
 System Name	___SRV1
 System Manufacturer	IBM
 System Model	IBM eServer x3400-[79742BU]-
 System Type	X86-based PC
 Processor	x86 Family 6 Model 23 Stepping 6 GenuineIntel ~1861 Mhz
 Processor	x86 Family 6 Model 23 Stepping 6 GenuineIntel ~1861 Mhz
 BIOS Version/Date	IBM IBM BIOS Version 1.68-[SPE168AUS-1.68]-, 9/10/2008
 SMBIOS Version	2.34
 Windows Directory	C:\WINDOWS
 System Directory	C:\WINDOWS\system32
 Boot Device	\Device\HarddiskVolume5
 Locale	United States
 Hardware Abstraction Layer	Version = "5.2.3790.3959 (srv03_sp2_rtm.070216-1710)"
 User Name	SCA\backup
 Time Zone	Canada Central Standard Time
 Total Physical Memory	4,095.70 MB
 Available Physical Memory	2.41 GB
 Total Virtual Memory	10.08 GB
 Available Virtual Memory	8.38 GB
 Page File Space	6.25 GB
 Page File	C:\pagefile.sys[/font][/font]

I must also add that there is plenty of disk space available 10x the data that is being backed up.

Does anyone have any insight as to what could be the issue here?

Is there a list of exit codes and definitions available?

Thank you.

The latest version is 4.0.7.14.
If this is the one that you have, please reproduce the error again and then collect the debug logs for analysis.
Instructions can be found here.

Thanks