You gave me very little information to go by, in your original post. When someone has boot issues, I will take it from the very beginning and not assume that someone is doing the process correctly. The statement that you used the "Same Process" and implied that you were having issues with other discs, led me to believe that something was wrong with your discs or the process, or both. I provide the following for some more insight into the concern.

The main reason I sent you to the downloading faqs is primarily that a good many boot errors are self inflicted. I, and many others, have posted about these issues in the past and few people seem to think it makes much difference, until it resolves their concern. Checking the iso MD5Sum or using BitTorrent to download the Official files from the Official source is paramount. Burning the disc improperly is the next cause for errors. Burning SLOWLY is the key. I have advised people on this ad-nauseum. Burning slowly allows the laser to make a better defined mark or "Pit" in the reflective surface. Some drives have trouble reading discs that were burned at a higher speed because they are less sensitive to the poorly defined marks made while burning at higher speed. All it takes is a good microscope to see the difference on a CD. Media is the next issue. If you burned the disc at higher speed, the speed is the most logical cause. If you burned at a slow speed, poor media compatibility is most likely your concern. Some drives do not burn certain media well. There are many different variables like dye color, dye type, reflective surface composition and reflectivity characteristics, along with the sensitivity of the reflective surface to the laser of the burner. Add to that the variables in the firmware calibration for different media. THEN you have issues with the READING Drives sensitivities to dye color, type, reflectivity, etc. It is prudent to use media that has proven to be compatible with BOTH the burning drive AND the reading drive. I have a notebook drive that is "supposedly" DVD-R AND DVD+R capable. It will only work properly with DVD+R media. It also prefers certain brands of media over others. Once I got that sorted out, the issues with that system went away. It is the same with many burners. Sometimes a firmware upgrade helps and sometimes not. Cheap garbage media is good for absolutely nothing but use as a small frisbee or reserved for target practice. Good quality Media is also important. I am surprised that the Verbatim Media did not work well for you, since I use +R and -R Verbatim with very few issues. I have also had very few issues with Memorex. It pays to check the drive manufacturer's site regarding recommended compatible media for BOTH the reader AND the burner and then testing some on your own drives.

There were a few posts regarding certain brands of drives with burning and reading issues causing boot problems. Enabling DMA using a cheatcode appeared to resolve the issue. If your drive requires DMA to be enabled, you must do so in the later versions of Knoppix since it is disabled by default. (Cheatcode is "Knoppix DMA") It can affect BOTH reading AND Writing functionality of the drives in question. The Memorex drives were not mentioned, however.

There are several good disc verification tools out there. I use the "Verify" option in Nero, but have used the Disc Inspector program from VSO Software with decent results. I use it with the drive that will be reading the disc to ensure compatibility. There are a few others, but I will not recommend them since I have too little experience using them to know if they are effective or not. It may also be a good idea to use one of these programs to identify the actual manufacturer of the media you are using. Some media is packaged and sold under certain brand names, but can be of widely different origins and manufacturers.

I am glad to see that you did resolve the concerns and appreciate the post regarding your solution.