Just saw this thread and thought I'd share my experience with this problem - which is lots. I developed this early in 2008 and although I hate to say it, it's something that really doesn't go away and you have to manage - at least that's my situation. For me, it was definitely poor mobility in the lower leg, specifically the peroneus longus, that caused the problem. It got so tight I got micro tears in the connective tissue between the muscle and the tendon itself, the result being that my whole achilles area got really swollen and in fact crepitus set in .... this had me going to physio at the local hospital and took ages to settle down.
I think when people talk about peroneal tendinitis and peroneal tendonitis they mean the same thing. The peroneal tendon is very extensive and if you have problems, you'll feel it referring everywhere, under your metatarsals, ankle, the lot. It's mean. It does respond very well to deep sports massage, but you have to be careful, particularly in the area around the retiniculum - the "strap" that holds the whole caboodle to the lateral side of your foot. Blood supply here is terrible, so a regime of combined heat/ice helps a great deal. I used to get up 15 minutes earlier, nuke my heat bag and then sit eating my breakfast with foot up, alternating heat/ice. Ibuprofen gel (10% stuff like Ibulieve) also helps.
I was very fortunate as my missus was training to be a sports massage therapist at the time this developed, so she's become a bit of an expert on peroneal tendon treatment. I hasten to add she's qualified now, but I still have to have regular maintenance. For instance, I biked on Saturday and ran 13 miles on Sunday .... that bloody muscle siezed up again and if she hadn't worked it, I bet it would have reappeared.
So I hope this helps. BTW, rolling a golf ball under you foot also helps relieve the pressure. PM me if you need to hear any more ..... hope it clears up quickly for you.
Martyn