Hmm it could get rid of the Y/C delay on the 72.
The webpage is slightly typed incorrectly since Kevin T had a slightly different interpretation, but the firmware is in fact correct form what you typed out.
It's suppose to be written as 70B608/70H329/71B273
This is one of the typical problems which some of the units will expereince. After the unit upgrades, for some reason the completed screen never comes up as it displays the blank screen. If it stays like that for an extended peorid of time, just turn off and power it on again. Since you already did it, you now know what happend.
When put the disc in for the second time, bascially what happened is that the unit's firmware was checked and since the unit is already up-to-date, the recovery porton of the disc was invoked. This essentually is suppose to bring up the completed screen but once again you experienced a black screen.
Hope this solves your questions