this was a pain in the neck, but after 5-6 hours researching the following worked for me:
Shane adair's advise as below ( from thread upstream) and
http://docs.info.apple.com/article.html?artnum=301182
shane thanks!
How to uninstall FCP 5
Here's the way to do it:
1) Close FCP
2) Go to: /users/username/library/preferences/
a. Delete the com.apple.FinalCutPro.plist
b. Delete the FCP User data folder.
3) Go to: Applications
a. Delete FCP application
b. Delete FCP HD addition easy setups folder.
4) Go to: /library/applicaton support/fcp system support/
a. Delete Custom Settings folder
b. Delete Plugins folder
5) Go to: /library/receipts/ and delete the following:
a. AnalogPAL.pkg
b. AppleIntermediateCodec.pkg
c. DigitalPAL.pkg
d. DVCproHDCodec.pkg
e. FinalCutPro.pkg
f. FinalCutproHDUpdate4.5.pkg
g. FinalCutProHelp.pkg
h. HDVCodec.pkg
i. IMXCodec.pkg
j. Uncompressed422.pkg
k. VideoOutSupport.pkg