There are 2 other things you can try:
- Adjust the replay buffer size on the soundcard settings tab, it defaults to 32k but try 16k and 64k to see if either helps
- Try the low latency output mixer from Mandolane,
http://www.mandolane.co.uk/swM3DMixer.html currently it is a free beta version but only to the end of April. However if you are using the Mandolane midi library the mixer will be free.