A recent FAA AD urged Boeing yet again to do something about the Cabin Altitude Warning which is still being misidentified by flight crews - also see the comment in Flight International 18 - 24 Nov.
The UK CAA did audit the airline under contract and were satisfied that Helios Airways was in compliance JAROPS at the time of the accident and recommended continuance of the AOC. The AAI&ASB Report Findings identified no shortcomings with the Aircraft or crew.
Regulators don't come much better than UK CAA and if they say it was OK, that's fine by me
