I'm having the same issue on Win 7 x64, but I double checked and ImgBurn isn't running as Admin. I'm pretty sure this was working fine until I updated to version 2.5.6.
FYI, I get the same very long hang in the "Creating Graph Data Thread" on my Lenovo T60 with a HL-DT-ST DVDRAM GSA-4083N drive.
11:29:39 BURN-Proof Enabled
11:33:34 Filling Buffer
so around 4 minute hang.
Are any of these switches available via the command-line options? I'm building a CD automatically and getting a error that my directories are more than 8-levels deep.