Please excuse the 'me too me too', but it just so happens I am having the exact same issue right now.
ANTS shows that the Private Bytes, Page File Bytes, and Virtual Bytes are all increasing at the exact same slope, but the Working Set and Bytes in all Heaps are stable.
Private Bytes and Page File Bytes are superimposed on each other with Virtual Bytes somewhat higher, but again, on the exact same slope.
Can someone name the beastie I am hunting for?
Thank you for your time,