Brief Buzz when operating AA 3.1

Every now and then there's a brief 2 sec harsh buzz when playing / recording AA 3.1. Test: this happens on demand - whenever I run another program with AA 3.1 in motion. Checked Sysinternals (Win XpPro) to see pgms are not running that are not needed (ie update). CPU is hardly being used. FreeRam XPPro 1.52 - says mem load is 29% (of 2GB Ram).

How can I stop this buzz? Multitrak - can't increase buffer in 3.1 as you can in AA 1.5.

Replaced the digital converter - now using Gina 3G. Works super fine.