I have the same issue. It started on ios 4.3 with my 3gs. I upgraded to an iphone 4s and the problem followed. Then I restored my phone and did not use a back up (for a clean phone) and it started again after 2 weeks. Went to Apple store and got a replacement phone that lasted a week and am having the problem start up again.
It's not just 3rd party apps. I can't use Safari, Messaging, Phone, or even the settings app without it crashing back to the home page. When I go to the diagnostics page, I see that every crash generates a lowmemory diagnostic page.