I had a similar problem with my Maxx loosing connection while on wifi at home. I just got the phone on the 28th and after the ICS upgrade a couple days later I noticed when I was at home I would not get email on the phone and the clock widget would stop the time not to long after I got home. It should be noted that it is not set to drop connection after inactivity and I do not have any smart actions set.
After several days of this and several calls to Verizon for assistance without resolution I noticed that when I was at home the little wifi indicator bars were all white, but when I was at work they would be blue. All white seems to mean you are connected to a wifi but there is no data connection.
When I moved a couple months ago At&t gave me a new router/ DSL modem in one unit, I believe it’s made by Netgear. No problems with any of my other devices connecting (2 laptops, previous phone was a BlackBerry). Pulled out my 8 year old Belkin router, plugged it in to my new router and connected the Maxx to that. Blue bars again but now I have 2 home wifi networks. Verizon still has no explanation, anyone else notice an issue with ICS and Netgear routers?