It could be caused by a corrupted ISO or bad name of a game.
Update webMAN MOD to the latest build using the online updater, reboot, uninstall webMAN MOD after reboot to remove all related files.
Unplug all USB devices from the PS3 and refresh the game list. If the problem persits, also rename the folders in the internal HDD:
/GAMES, /PS3ISO, /PS2ISO, /PSPISO, /PSXISO and /ROMS
Reinstall webMAN MOD. After you get the game list displayed on XMB, rename the folders to the original name and plug back the USB devices. It's recommended to do this gradually (rename just one and refresh the game list) until you identify which folder is causing the freeze.