I tried a different DVD drive (USB) and ImgBurn worked. I also tried creating the ISO with the original internal drive and other software (InfraRecorder) and was successful. I guess there's something about ImgBurn paired with my internal drive that's causing a problem. Here's the data from the disc info box:
PLDS DVD+-RW DU-8A5LH 6D1M (RAID)
Current Profile: DVD-ROM
Disc Information:
Status: Complete
State of Last Session: Complete
Erasable: No
Sessions: 1
Sectors: 1,553,337
Size: 3,181,234,176 bytes
Time: 345:13:12 (MM:SS:FF)
Supported Read Speeds: 2x, 4x, 6x, 8x
Current Read Speed: 1.7x - 4x
TOC Information:
Session 1... (LBA: 0)
-> Track 01 (Mode 1, LBA: 0 - 1553336)
-> LeadOut (LBA: 1553337)
Track Information:
Session 1...
-> Track 01 (LTSA: 16580608, LTS: 1, LRA: 0)
Physical Format Information (Last Recorded):
Book Type: DVD-ROM
Part Version: 0
Disc Size: 120 mm
Maximum Read Rate: 2.52 Mbps
Number of Layers: 1
Track Path: Parallel Track Path (PTP)
Linear Density: 0.267 um/bit
Track Density: 0.74 um/track
First Physical Sector of Data Area: 0
Last Physical Sector of Data Area: 0
Last Physical Sector in Layer 0: 0