According to Sony not even everyone who got the 4.45 update was affected. They said it was a small number of people who got that update who were having problems.
That was just PR double speak and relative to the fact that only a small number of PS3s (out of the total user base) even tried to download and install 4.45. They didn't specifically say that of the users that downloaded and installed 4.45 only a small number of them were affected. Sorry to nit pick, but I found Sony's only official response (which can be read either way) somewhat dismissive, offering no reassurances that they can and will fix people's bricked systems:
In a statement provided to VideoGamer.com, a SCEE representative said that the firm was "aware of reports that the recent PlayStation 3 system software update (version 4.45) has caused the XMB to not display on a small number of PS3 systems.
"We have temporarily taken 4.45 offline and are investigating the cause of the problem. We will announce when the system update is available for download as soon as possible."