I have same exact problem. If you find fix, pls share w/ me at spmisc@dslextreme.com. If you email me, I will do the same if I learn something.
I also noted that if I call IVM on my cell it picks up after 7 rings (IVM is set to 4). Another frustrating problem.
Am trying to reinstate my paid customer support with NCH - without it there is little chance they answer emails.