I've had this issue before where the sims in my game freeze but the effects continue and solved it by using porter to take them all to a new town. I'm on the forth generation and like to keep my family tree intact. I've been having the same issue with sims and time freezing but effects continuing, except it doesn't unfreeze now and i'm forced to force quit the game, this happens about 3 minutes into playing. I have overwatch, errortrap, the traffic mod, and GoHere, and none of the save cleaning advice from other threads has helped.

Is ErrorTrap kicking up any script logs that we could help you interpret at NRaas?
http://nraas.wikispaces.com/How+To+Upload
(free registration required to upload and open up a support thread)

If not, it sounds like you either have a mod from another source that is misfiring upon startup (3 sim minutes isn't very long or do you mean real time minutes) or there is some in-game event that is scheduled to happen at that precise time that is getting things stuck. One common one is a sim somewhere in town giving birth and getting stuck in a loop, NRaas Woohooer fixes that one. The Hospital Overhaul mod is also known to cause this, among other things.

You might also consider adding MasterController and doing an MC Reset Everything from City Hall, if you can manage to pause the game clock once it's all loaded up but before the freeze.

Just for the record or whatever, not everyone needs to Porter up and abandon ship every few generations. Many of us do manage to hold onto our homeworlds for as long as we can stand to play them, though it sure is a lot of work keeping things moving smoothly over time.