Blank CD-RW Media

[puget93]

I've searched this forum, Google and called Lenovo trying to get the answer to what seems like a fairly simple question. But, I've had no luck, hoping someone here is knowledgeable about optical drives and blank media.
I have a ThinkPad R60 model 9457-95U. The optical drive is a "CD-RW/DVD-ROM Combo Ultrabay Enchanced Drive", P/N 73P3275. I want to backup my data files to a CD-RW disc and took considerable time to research my optical drive specifications to be sure I purchased the correct blank media. The speeds for my machine are 24X/24X/24X/8X. So, I felt confident buying blank Memorex 24X CD-RW media (Ultra Speed). I used the pre-installed ReadNow software which returned a prompt stating "The media you have inserted is read-only". After checking for driver and program updates and checking the drive in Device Manager, I ran PC-Doctor's Rewriteable CD Test which failed. I thought the discs must be defective so I called Memorex and got nowhere. I found a Lenovo web page titled "Information about CD and DVD media types-General". The information under CD-RW drive states "CD-RW drives that have the ultra speed designation on the logo are capable of recording on 24X CD-RW discs." Then under CD-RW/DVD-ROM combination drive (what I have) it states "this drive can record on CD-R discs and standard-speed CD-RW discs." Standard speed is not 24X that I can determine. Every 24X blank disc I've found has the Ultra Speed designation. Also, my drive door has a DVD-ROM logo but only "CD-RW" in letters with no logo. Should I buy Standard Speed (2X-4x) blank CD-RW media only or does 24X imply that I should use Ultra Speed? Sorry this is so long and thanks in advance for your help!