I have the opposite problem. Just upgraded with the latest firmware (released 3/10/08).
Burned the ISO image to a CD and I was off and running. I once struggled doing the same on my HD DVD player when I finally discovered I was trying to use a blank DVD to burn instead of a CD.
I can still not get internet access through the 5000. Using the same DHCP ON and Auto settings I use for my XA1 and Dish DVR. Both work well through a wireless ethernet connection. But not the 5000. It will not connect.
I like the player otherwise. I used the re-endcode for DTS 5.1. Good enough for now. PQ is excellent!
I've tried a few different formats and all were glitch free except a BD copy of Hit Man.
It froze about 1 hr into the movie.
I was able to power it down (no resetting) and start again, where it finished the movie just fine. Not sure what happened there. But have had occasional freezes on my XA1.
Not common though.
Build date on the 5000 is 01/08