Commiserations APE.
I'd definitely have a think about the footwear you're wearing when running. I got some Mizuno Wave Harriers recently, and after a couple of runs my PF was coming back. I swapped them for the Mizuno Wave Ascends (I have a bit of a Mizuno fetish at the moment) and it's been behaving since then.
When I'm recovering from injuries (frequently), my doctor has me follow the following schedule to get back into running.
Day 1 : alternate run 45 seconds, walk 15 seconds for 5 minutes
Day 2 : run 45 seconds, walk 15 seconds for 10 minutes
Day 3 : run 45 seconds, walk 15 seconds for 15 minutes.
Day 4 : run 45 seconds, walk 15 seconds for 20 minutes.
Day 5 : run 45 seconds, walk 15 seconds for 25 minutes.
Day 6 : run 45 seconds, walk 15 seconds for 30 minutes.
Day 7 : run 45 seconds, walk 15 seconds for 35 minutes.
Day 8 : run 45 seconds, walk 15 seconds for 40 minutes.
Day 9 : run 45 seconds, walk 15 seconds for 40 minutes, including 5 minutes non-stop running halfway through.
Day 10 : run 45 seconds, walk 15 seconds for 40 minutes, including 10 minutes non-stop running halfway through.
Day 11 : run 45 seconds, walk 15 seconds for 40 minutes, including 15 minutes non-stop running halfway through.
etc etc until you get to 40 minutes non-stop running.