I previously tried the 2.0 version, now 2.1
Under Vista x64, neither mp3 nor aac files will play.
Basically I can load them into the track list, drag to the player, and hit play, but the time remains on -00:0:00 and no audio is produced.
Hello Guest,
currently UltraMixer does not natively support 64 bit Windows as many applications do 
So most of them claim to be 64 bit compatible but that’s not true. Indeed UltraMixer runs on 64 bit Linux since almost 2 years fluently.
The trick for every other software is just using the WOW (Windows on Windows) technology for XP64 or Vista64.
Common applications does not require special attention. Since UltraMixer uses a Middleware that’s called Java Runtime Environment you would have to make the right choice. In case you what to run the 32-bit UltraMixer Version on your 64-bit Vista, you would have to install the 32-bit version of the Java Runtime Environment (JRE) (http://java.sun.com/javase/downloads/index_jdk5.jsp)
with best regards
Sl@jaR