4x DVD+RW on my 2x DVD+RW drive?

I went out and bought myself some new DVD+RW's around christmas time and I can't seem to get them to work in my drive. I have an older drive (I/O Magic DVD+/-RW Dual Format 4x). In the user manual, it says it burns 2x DVD+RW. I bought some Memorex 4x DVD+RW disks thinking they were backwards compatible (speed-wise). When I insert the disk, Roxio 6 won't recognize the disk as a RW. I can burn to the thing like a regular DVD+R and it works fine. When I try to format it with Drag-To-Disc, it says it's not a rewriteable disc... When I try to just drag and drop with WinXP, it says the disk is Read-Only... any ideas?

EDIT: I have downloaded and installed the latest firmware... it seems the drive is a I/O Magic, MagicSpin and a BTC drive. It came in an I/O Magic box, it says MagicSpin on the drive itself and the firmware was BTC firmware. All three companies put out a "1004IM" drive...

have you tried Nero?

I have tried Nero, Roxio and Alcohol 120%

flash the firmware of the drive and try again.