In case anyone is interested, I just noticed a changelog posted over at Nero - the first one in like 2 years or something. I imagine it only covers the most recent changes and not all the intermediate versions since the last changelog, though.
http://www.nero.com/nero6/enu/Nero_Burn ... es.html#a1
Version Number: 6.6.1.15
(Changes from Package #1, Version 6.6.0.16 ? 6.6.1.15)
Release Date: March 13th, 2007
Other Changes/Bugfixes
* Erasing a DVD+RW was not always possible´
* The error message “cannot connect to TRF” was displayed when burning a UDF 2.50 disc
* Burning a compilation to image recorder was not possible in specific cases
* The Internet database could not always be accessed correctly