I gotta say that I haven't been experiencing any commercials freezing in a while.
The only advice I can give anyone is that during the period I was frequently experiencing this i.e. there was a two / three month period where I could not watch any CBS show from the xfinity streaming service without the commercials freezing I was always able to go to the CBS website and watch from there without any issue. I still go to the CBS website frequently because for some reason some shows like Elementary and Blue Bloods show up a lot earlier there and almost a day later on xfinity.
I swapped my modem a couple months ago from one of those junky RCA modems (it was locking up and I was getting very poor performance) to a newer Moterola model; I use a Linksys E3600 router and I haven't had any problems since.
- Norm