Well I received the new media I mentioned above, the Verbatim DVD+R DL. As mentioned above the box DOES say 2.4x. However, I was able to do the following:
Burned 2 UDF format DVDs (8.5 GB) at 2.4X, no errors.
Burned 2 UDF format DVDs (8.5 GB) at 4.0X, no errors.
Burned 6 UDF format DVDs (8.5 GB) at 6.0X, NO ERRORS!!!!
All DVDs were burned using Plextools Professional XL V.3.08 and data verification, autostrategy were both on.
Apparently all my troubles have been caused by a selection of poor media (RITEK D01)
These Verbatim DVDs I got from newegg are great, and the cost was quite reasonable as well. For those interested, the Manufacturer ID is: MKM and the Media ID is: 001 This is the link (once again) for the most excellent media I bought from www.newegg.com: http://www.newegg.com/Product/Product.asp?Item=N82E16817131163 Keep in mind that Newegg.com also sells the bad RITEK D01 media from Memorex so stay away from those unless you want a bunch of coasters.
I want to thank all the really great people (especially Buck!) here who have given me so much good advice in the past few days. You guys are great!