I purchased and installed the Lucida package, and there was an error message in an ams symbol file that \Digamma was already defined.
This error results from conflicting declarations of AMS symbols in the lucimatx and amssymb packages.
Fixing this is easy: Omit the loading of the packages amssymb and amsfonts! You will still be able to use the AMS symbols, since the lucimatx package already makes them available. Note that the use of amsfonts/amssymb together with lucimatx does not only result in error messages, but may also lead to wrong fonts being used in the output (CM in place of Lucida).
See also section 6.6 (AMS symbols) in the lucimatx documentation.
(answered by Walter Schmidt)