Hello,
When I click on the Dock's icon, the app seems to be opened, but it's closed in few seconds. To solve this, I've try to erease "com.apple.finalcutexpress.plist" and "Final Cut Express User Data" folder. No way.
2. Removing receipts and reinstall Final Cut Express, and updating to the latest version, but no way.
The machine: Power Mac G5 Quad with 4.5 Gb of ram and 1.5 Tbyte of hdd. (10.5.8)