Japanese developer Bu-nyan has posted on his page (linked above) the following:
Roughly translated, tmaster has concluded the following:
"FW2.50 not start in the BD-J.
Upgrade to stop so we can update orz"
I don't know if Bu-nyan is saying its ok to upgrade or not.
Update: I can confirm that bd-j don't work with 2.50. I tried it on my brothers ps3 and it gives me an error. good thing I still have mine at 2.43 to play java.
Why sony stopped I don't know.. maybe a hack, who knows?
More PlayStation 3 News...
FYI, although most of the PS3 Devs are sleeping CJPC said the following on IRC:
That being said, it may explain why Bu-nyan and others are reporting BD-J as not working... when 'something' just may need to be tweaked/updated for it to work again versus Sony blocking it.