Although I also am quite critical of Sony/Columbia/BMG these days for their antics with music cd releases, I seriously doubt that anything like you are describing is being caused by something Sony has managed to do to your DVD burner.
What you are describing sounds more like a compatibility problem within the combination of burner, media and burn speed. I used to use a Sony 510a dvd burner, but had to retire it because Sony can't be bothered to offer firmware updates for it - so it is horribly unreliable with 8x and faster media. Maybe Sony is too busy shoving malware and rookits on their music cd's to support their dvd burners. And the 510A is not rated to handle any RW media at 4x.
I suggest you try using some media specifically indicated as supported by your Sony dvd burners - and burn at a slower speed than the maximum indicated as possible. For example, try burning at 2x with a burner and media rated for 4x. You might peruse videohelp.com to find a listing of users experiences with particular media in your particular dvd burners.
Specifically for your 510a - make sure it has the last Sony firmware made available in it - 1.1a, I believe.
http://sony.storagesupport.com/dvdrw/dru510adwn.htm
The 510a is a maximum 4x burner. It's burn speed is more controlled by its firmware than anything you tell it via the burning engine program. Try downloading and installing the "speed control" module available on the Sony website. Set it to "silent". This will slow down the burn speeds, but I found it to increase quality dramatically. Try using Ritek 4x DVD-R media (G04) in it. That media was always VERY reliable in my 510a, with the "speed control" module set for silent. You can still get it at meritline.com, I believe.
http://meritline.com/ritek-ridata-4x...dia-discs.html

The other alternative is to move to a different product line - like I did - I am very happy with my Benq 1620 drive, and if I was in the market for a new burner today, I'd be looking carefully at the Benq 1640 and 1650 drives.

So - in summary - for your Sony 510a:
. firmware 1.1a
. speed control module installed and set to silent
. burn some Ritek 4x G04 media at 2x
. see if the quality of your burns isn't significantly better