The most common complaint with HEN 4.90 is multiMAN crashing to a black screen on launch. Do not launch multiMAN immediately after activating HEN. Wait 10 seconds. If it persists, delete multiMAN, rebuild your database (Safe Mode > Rebuild Database), and reinstall the Full package.
Before installing or running any homebrew, you must activate the enabler: Boot your console : Navigate to the column on the XMB. Enable HEN : Locate the Enable HEN icon (often looks like an egg) and press multiman ps3 490 hen full