Sony today released system update 4.46 for PS3 consoles. Firmware update 4.46 was released to fix an issue in firmware 4.45 which removed the PS3 main menu (XMB) after the 4.45 was installed.

New for 4.46

You can now hide notifications when you earn a trophy. 

An issue in which the XMB™ (XrossMediaBar) menu is not displayed after updating the system software to version 4.45 was observed. This version of the system software addresses this issue.
If the XMB™ menu is not displayed, you must perform the update by starting the system in safe mode. 

If you had this problem with 4.45 and cannot access to the XMB to download the update, you’ll need to boot up the PS3 in safe mode and manually download the latest update from you computer. The instructions and download files can be found on Sony’s support website.