These are DVD-RW. My recorder only writes to DVD+RW. After convincing my girlfriend that it wasn't my fault, I was able to swap them with a pack at work (our DVD writers aren't as fussy) and they work fine in the right drive (likewise the right disks work fine in my drive).
I have since done the research and the difference comes from way back when DVD's were first being invented. There were 2 different teams of developers, one team created the DVD-R/RW disk and the other invented the DVD+R/RW. DVD+R/RW disks have a very slightly higher capacity, but DVD-R/RW disks are cheaper to create. DVD-R/RW were developed by Pioneer and are supported by Apple, while DVD+R/RW are supported by Sony, Microsoft, Philips, Dell and many others. Most new drives support both but just make sure you check.
In summary, these are great disks if they are the right ones for your drive, just don't be a plonker like me and assume you know best.
