This error may occur in version 4 build 116 and earlier when you are burning in IMAPI mode. Get the latest version of Acoustica MP3 CD Burner Here.
You can also fix the problem by clicking on the MP3 CD Wizard button (to the right of the Song List) and specifying that no filenames are longer than 31 characters.
Finally, if your drive is supported by the Goldenhawk burning engine, you could turn off IMAPI. Click on the File menu, select Preferences and in the CD/DVD Burner preferences, uncheck the "Use IMAPI" option.