robot4rip won't rip DVD

[DevilsChild]

Hi,

I'm getting some errors using robot4rip. When I try to rip "American Graffiti," it shows the following errors and the green "start" arrow goes blank (won't start the rip):

3:59:00 AM: TheWEFs robot4rip Version 0.4.0.1087 started
3:59:00 AM: System is WinXP (5.1.2600.2)
3:59:00 AM: Settings loaded
3:59:00 AM: Enumerating drives
3:59:00 AM: Found drive D:[GRAFFITI], found VIDEO_TS folder
3:59:00 AM: Found drive E, the drive is empty
3:59:00 AM: Found drive F, the drive is empty
3:59:00 AM: Found drive H, the drive is empty

3:59:00 AM: Scanning "D:\VIDEO_TS\"
3:59:03 AM: Parsing "VTS_01_0.IFO"
3:59:04 AM: Warning: No vobs found for "VTS_01_0.IFO"
3:59:04 AM: Parsing "VTS_02_0.IFO"
3:59:04 AM: Warning: No vobs found for "VTS_02_0.IFO"
3:59:04 AM: Parsing "VTS_03_0.IFO"
3:59:04 AM: Warning: No vobs found for "VTS_03_0.IFO"
3:59:04 AM: Parsing "VTS_04_0.IFO"
3:59:04 AM: Warning: No vobs found for "VTS_04_0.IFO"
3:59:04 AM: 4 Ifo-Files

This is the first time I've experienced this. What could be the problem?