DVD burner problem

I have an NEC 1100a DVD burner running on Win '98. It plays all disks, burns VCD's and even burned the test disk shipped with it just fine. The problem is burning other DVD's. I have tried both Memorex and Maxell DVD's and tried Nero 6, Easy CD Creator and Sonic DVD software and none are able to read the blank media. I have not been able to find out what type of disk came with the unit since that was the only one to actually burn. Any help would be appreciated since I am new to burning DVD's.

welcome to windrivrs fultilt1

this is where the firmware upgrades should be if it was working.... give it a try in a while. If there is a firmware upgrade, then try that.