To jtrainer: I have installed avast free 2014.9.0.2006, and I had exactly the same problem: every time I tried to create either usb or cd, both seemed to work but at the end none of them were created. I live in mexico and I use w7sp1 ultimate in spanish so avast also was installed in spanish. I did what giogio mentioned, I mean I installed the English language to avast and switch avast to english GUI and voila! I was able to create both USB and CD .iso file.

Maybe you might try to install avast in spanish in first place, then add english language to avast, switch avast to english and finally try to create usb or cd.

Thanks giogio for the tip of installing english language to avast. Finally after several moths of googling about this issue I was able to create usb/cd bootables. I bought AVAST Rescue CD more than one year ago but it has errors, for example: I cannot choose what drives or folders to scan the program terminates abnormally and crashes.