The burst rate is fine. You use microsoft drives, also fine. Your nero 188.8.131.52 should be updated. You have various filter drivers installed, which could cause problems (like blue screens when insering media), but your problems seam to be media and speed dependent.
Your guess is right, the drive does not like to burn at low speeds. Burn the RITEK R03 @8 or @12, the CMC MAG F01 @8x.
CMC MAG R01 is not supported by the firmware, so a default strategy is used. You might get better results by swapping the write strategy, but first check that the other two media types burn fine.