811s and CD-Rmedia

I’ve got an 811s (I think, Nero reports it as a DRW-1S81) and have found that cd-rmedia’s 4x own brand disks (www.cd-rmedia.co.uk) will only burn at 1x, while the same disks work fine on my girlfriends 851s. I’ve also found the same thing with a TDK 4x disk, though not tried one of them on the 851. will a firmware update fix this or am I better off sticking with another brand of disk (burns 4x on all other brands I’ve tried)

er…forgot to say this is with DVD-R disks, I gather +R cause less problems but my standalone Panasonic DVD player prefers -R