I trust you've tried different blank media?
Only kidding. On a serious note, I had a similar problem with my Ricoh
8x8x32 CDRW. It just refused to even recognise that a blank disk was in
the drive, but it would read other disks fine.
In the end, after several calls to Ricoh tech support, they deemed it to be
a hardware fault and RMA'd me a new drive the next day.
Give Acer tech support a call just in case.