http://www.sugarglider.com/glidergossip/topic.asp?TOPIC_ID=16179
Mine wound up being from my potted plants after I had repotted them with new soil. One place they never were was the glider room because their door is always closed. It took me forever to get it under control. After this post, they came back and I finally traced it to the plants, got rid of them and the
flies went too. That may not be the issue with yours, but there are some tips listed that might help.