To your right you will find that the "new list gen" link has been replaced with the Universal List Gen. This new version will auto-detect your mame version and react accordingly. This should fix any problems caused by 99u4 (actually that version has been pulled, but 99u5 will have the same issues). Simply replace your listgen.exe in the "list generator" folder with this one and you should be good to go.
Also this version *should* work on older versions of mame (pre .84 old) but I haven't tested it.
Some email feedback about how this new listgen works would be appreciated.
The latest version of mame removes several calls, many of which are used in johnny5 and the dk listgen. Upgrading now will cause those apps to fail!!!
I am working on solutions to both, so sit tight.