I'd like to bump this thread because I have created several dozen voicepacks for the old UT (UT99 as you call it) and I need to convert/import them to UT2004. When I try to open the old UT .UAX files in the UT2004 UnrealEd it crashes.
Do I need to export all the .WAVs, import them in UT2004, save .UAX, then re-point the voices, compile/save .U? Essentially recreating them from scratch?
Are the commands similar in the engine I could just change the .INT file?