Did you test this version? For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.
You state that this is an AVI, but mention an mp4. Are you referring to export formats that produce slow audio, rather than the initial load failure issue?
If this persists, please upload and share - per the instructions above. Someone will test your file.