PlayStation 3 firmware update 2.41, a fix for the problem-plagued 2.40, is officially live now, and SCEE has released an official statement explaining just what happened:

"The PLAYSTATION®3 (PS3™) system software version 2.41 is now available for update from July 8, 2008. With this update, we have fixed the problem that prevented a limited number of PS3s from activating properly after updating to version 2.40, when certain system administrative data were contained on the HDD.

The statement continues:

For those users who have updated to version 2.40 and have experienced the problem that XMB™(XrossMediaBar) is not appearing, or no images are displaying on the screen, please contact Customer Service.

We have confirmed that for those users who have successfully updated to the version 2.40 and are able to activate the PS3 system, this problem will not occur on your PS3.

We apologise for any inconvenience this may have caused you and appreciate your understanding and continued support."

So, problem solved, it seems? Personally, I think it's pretty cool they were able to roll out a fix so rapidly. And we get platinum trophies!
Firmware 2.41 announcement [Three Speech]