ok, i just tested 2.3.1.0, and now it does not hang, however gui begs for a volume label, but i did include that in the command line, like:
imgburn /BUILDMODE IMAGEFILE /MODE isobuild /FILESYSTEM "udf" /VOLUMELABEL "my_test" /ROOTFOLDER no /NOIMAGEDETAILS /CLOSE /START /SRC "f:\testproj.ibb" /DEST "d:\test3.iso"
edit: never mind, found the problem, just had to clean the ibb a bit, so it only goes like:
IBB
[sTART_BACKUP_LIST]
C:\Fraps
C:\Python24
C:\totalcmd
[END_BACKUP_LIST]