[haus]

What's your audio adapter (what does it do and who makes it)? Maybe if someone else has the same equipment they can indicate if they've had the same problem. Sounds like a hardware problem or incompatibility. If it's some sort of car kit I could definitely see this happening as you might have an external interface to answer, reject, and redial/return calls with one-button interface, the same way double-tapping a BT headset button often redials (or something similar, depending on the headset).