I have the exact same problem. Here goes what I get from terminal:
Code:
$ prl_convert "/Volumes/Externo 1TB/VirtualBox VMs/Windows 7/Windows 7.vbox" --dst="/Volumes/Externo 1TB/Parallels" --err-code --reg=y --no-hibernate-check --force
objc[15697]: Class MethodInfo is implemented in both /Applications/Parallels Desktop.app/Contents/Frameworks/libPrlXmlModel.1.dylib (0x1013de918) and /Applications/Parallels Desktop.app/Contents/MacOS/prl_convert (0x1005c93e0). One of the two will be used. Which one is undefined.
objc[15697]: Class DeallocHook is implemented in both /Applications/Parallels Desktop.app/Contents/Frameworks/libPrlXmlModel.1.dylib (0x1013de940) and /Applications/Parallels Desktop.app/Contents/MacOS/prl_convert (0x1005c9408). One of the two will be used. Which one is undefined.
Conversion progress: 0 %
ErrorCode: 0x80045003
Seems like prl_convert is crashing because there are classes with the same name both in a library and in its binary.