Burn dvd in dual layer

[qanda]This thread is about the Lite-On DVD RECORDER DVD+R RW. Click here to see full specs[/qanda]I have a iHAP422 DVD RW in my computer tower my problem is that i can burn regular DVD 4.7 GB but it wont burn DUAL LAYER , I was able to before have tried contacting LITE ON SUPPORT they are no help anyone have any suggestons, One more thing when i try to burn dual layer disc i get the following message

there was a problem writing to the disc, you can try again by clicking the retry but, you will need another blank disc ready

ive tried still the same out come disc are brand new DVD+R DL Mfg ATIVA