I bought a BDP5200/12 a couple of months ago. On the first powerup it wanted to upgrade fw to 1.55, and i let it do so. Later I discovered that it froze completely as soon as I tried to enter the advanced menu. I had a discussion with philips support and after trying this and that they adviced to return the unit to the reseller. I did so and got a new one, wich worked fine. Of course I didn't upgrade the fw this time from the start and I don't dare to now either! Not to 1.55 anyway, maybe if a new fw is released....
If anyone else have had this issue, please post so that Philips is made aware of the problem!