Every day my VOIP adapter device (Dlink, which I used with VOIP.MS for the past 18 months) needs to be rebooted. All of a sudden the device is not registered anymore (and the phone has no dial dial tone) and needs to be rebooted.
Sounds more like a defective ATA... Had similar problems with my Linksys PAP2T. Worked ok for a while and then it started doing weird stuff.
I replaced it with a OBi100 a few months ago and now everything works well again.