My local Sony service tech showed up this morning and provided what seemed to me to be a very convincing fix for my kds-60a2000.
First, he told me that he'd already personally done service calls to this fix particular type of problem 3 times prior to my service call. So this problem is quite wide spread. Second, he told me that Sony shipped about 5000 kds-60a2000 with this faulty fan. He said the problem is a connection problem in the fan (molding attached too tightly as a fan production problem or something) which could be sometimes fixed with vibrations in the set, thus the opening/closing door tricks which will sometimes fix this problem temporarily. The fan looked a lot like the fans in the back of a PC by the power supply. This is not the Nider (from Vietnam) fan visible in the back of kds-60a2000, but rather a bigger fan closer to the rear projection light. This fan has "Sony" printed on the fan itself and there was a Sony part number there, but the guy took the part with him (to return to Sony he said) and I didn't get the part number.
My premium service tech then replaced this fan with an improved part (not the same part number as before, but still a Sony-built part). He told that this part was never used in the regular production of the kds-60a2000, but WAS used the corresponding Bravia series (since 2 years) after Sony discovered this fan related problem.
I must say I'm still a little worried because I've now read posts of some people that got a fan replacement (hopefully not this improved fan) for a kds-60a2000 and faced the same exact problem 6 weeks later (again the 4-blink sequence). Again, they asked Sony to replace the fan, but I didn't find any follow-up for this case.
One other problem for me is that it took my Sony premium service 2 weeks to get the part from Sony and ultimately make this fix. I can't tell for sure, but it seemed like most of this delay was caused by a delay from Sony in shipping this replacement part.
Anyway, my kds-60a2000 is playing beautifully now, but this problem does indicate that a large number of SXRDs were shipped with faulty fan parts, and I'm sure there will be plenty of other owners who will struggle with this problem. On the good side, the service tech said that this fan has not gone into the Bravia models since two years now, so most Bravia SXRD owners are safe from trouble here.