Burning DVDs Slows System Clock?

I just installed a new NEC ND-3500A DVD+RW burner in my SuSE 9.0 system (Dell 600SC with SCSI hard drive but IDE DVD) and ran a master backup using the LoneTAR backup software. After completing both backup and verify passes the system clock had lost about 1 hour 40 minutes! Later, I burned about 600Mb and 200Mb to CDs using k3b and lost about five minutes. Is this a known problem? Do I need to look into renicing the backup processes to prevent this? Thank you, Lucky Leavell