I was just browsing through TDK's website and happened to come across a new firmware for the TDK VeloCD 48x24x48 Internal CD-RW Drive. The previous firmware was S7S5, while the newest version is S7S8. TDK claims this firmware upgrade will offer improved compatibility with a variety of recordable media.
You can look at it here
Also, since the TDK 52x firmware is on the TDK website, can I just flash my TDK 48x drive with it to write in 52x, or is there a more complicated procedure than that?