The reason for the writer to go for 4x, even if you want it to go for 2.4x, is that the firmware only supports that media at 4x.
That Verbatim media - is it on the box labeled - Made in Singapore or Made in 'elsewhere'?
That you have installed your friends writer in your own computer and that it fails, sounds as there is an issue with drivers or that the writer is connected to a plug that is not working well with writers. What model of motherboard do you have? Most times the Windows default drivers works best.
Your friends writer has a later firmware.
http://se.lgservice.com/index_b2c.jsp