Tools-Settings-Graph Data tab and look to see that your path for saving graph data is set correctly or tick restore defaults and let ImgBurn set it for you..
If it's not that someone will come along that maybe has a better idea.
In addition to what mmalves has written:
http://forum.imgburn.com/index.php?showtopic=8000
Are you using your system for any other tasks while burning? If so try burning w/o doing anything else.
OK try these suggestions:
Your media is junk, CMC is among the worst in the field. Read this.
Are you doing other things on the computer while you are burning? If so, stop doing anything and just let the program do its' thing before doing any other tasks on the machine.
Let us know how this works.