Nero has a tool included in your
Nero 7 called Nero CD-DVD Speed. Put a DL disc in the drive and fire that app up and click on the Disc Info tab. MID=Media ID.
You have an older drive and that might be it but if this happens on 2 pc's which i guess they have different drives i'd say it's a media problem. Unless any of those discs you have come up to be MKM001 or MKM003. Verbatim brand is really the only +R DL's recommended here. It's all i use and no problems here.