I was converting date columns in a log-table to the new timestamp datatype. This datatype is more precise and can handle milliseconds. After recompiling my Packages i got the errors
ORA-06552: PL/SQL: Compilation unit analysis terminated
ORA-06553: PLS-320: the declaration of the type of this expression is incomplete or malformed
There was no line that was wrong so this error-message didn't give me a glue what was wrong (i guess that's the sense of some oracle-error-messages "just to confuse the russians" 
).
The reason was that the column name was "timestamp" what is the exact name of the datatype. After renaming it to "timestmp" it worked perfectly.