Sony has released a new firmware
patch for the PSP to fix a small issue with the UMD Drives, here's the text of the fix:
Sony Computer Entertainment America today released the latest firmware update for PSP®(PlayStation®Portable) system, version 3.73. With this update, operation of the UMD™ (Universal Media Disc) drive has been improved to address cases in which the UMD drive occasionally suspends and fails to reload data. Updating the system software to version 3.73 will resolve this issue.