The error code you mention is:
-50 paramErr = Error in user parameter list
You won't find much in the way of direct help on the error code listing.
Tell us some more about your situation/system.
what OS are you running? Are you using iTunes, Toast or some other writing software? Is this burner a serial, USB, Firewire...?
This converted G3 has a sonnet processor hardware upgrade card? otherwise I'm confused by your "converted G3" statement.
Fill in some blanks and we'll galdly help. Between BuddingDesigner and I... no worries Mate.