Yes, it sounds like your drive doesn't work well with the Sony 48x media. My advice would be to try even lower recording speeds, such as 24x or even 16x.
These days, it's never safe to assume anything based on brand name. As it turns out, this Sony drive is actually made by Lite-On. BTW, Lite-On drives are very good.
I don't know if Sony actually makes their CD-R media, but I tend to doubt it. Unfortunately, you can't always assume that two products being sold under the same brand name will work well together due to this fact.