[antlr-interest] Error in AST

[Nourchn Nor]

I wrote one grammar on AntlrWorks but one error is shown when I add same
statement,
Here is the error: "error(211): Essai.g:87:16: [fatal] rule predicate has
non-LL(*) decision due to recursive rule invocations reachable from alts
5,6.  Resolve by left-factoring or using syntactic predicates or using
backtrack=true option"
And if I have correct by backtrack=true, the AST of every rule in the syntax
Diagram of Antlworks is consisted by { synpred1_Essai }? With Essai is the
name of grammar.
This is an error this  { synpred1_Essai }?  ? what can I  have to correct
him?
please help me