Please Help: ASUS DRW-22B1ST Can't write DVD+R?

This thread is about the Asus DRW-22B1ST, Black. Click here to see full specs

I've recently bought an Asus DRW-22B1ST and have it in an external USB enclosure attached to an iMac running the latest OS. I can't seem to get it to burn a DVD+R - every time Toast throws up a medium error. I've done several dozen Verbatim 16x -R's and yesterday it failed to write 2 Verbatim 16x DVD+R's. I tried writing the first at 8x and the second attempt was at 6x. Tonight I found another batch of Verbatim DVD+R 8x and it failed to write that one too. So far it has not been able to write any +R. I've got another brand new spool of 50 16x Verbs but reluctant to open it in case I need to swap it for another spool of -R's. Has anyone used this drive before? Thanks.

Obviously the chip in the external case is the issue......
Which one is it?

Thanks chef - I was wondering if it could be something like that. To the best of my knowledge by probing with the System Profiler and turning the offending drive on and off to see what disappeared and re-appeared;

Product ID: 0x2329
Vendor ID: 0x152d (JMicron Technology Corp.)
Version: 1.00
Serial Number: FFFFFFFFFFFF
Speed: Up to 480 Mb/sec
Manufacturer: JMicron

I'm fairly limited for choice where I live and the seller of the drive and case is a discount franchise so I assume that the drive probably wouldn't be the best...

Just to provide feedback on this I went to the JMicron site and downloaded software for os x. There wasn't much to choose from and I didn't know if it was applicable to my problem but I loaded the software and rebooted and the problem has gone away - discs that came from a spool that was previously failing are now writing fine. Fingers crossed and thanks for your assistance chef.

Oh, nice result!