shift/reduce conflict in cup parser

Question

I wrote this grammar:

/* Precedences */ 
precedence left UMINUS;
precedence left ID;

Expr ::=      ID:e              
    | NUM:e             

    | Expr:e1 TIMES Expr:e2     

    | LP Expr:e RP          

    ;

Call ::= ID:id LP  ExprComma:args RP  ; 

When I try to run the parser on this program:

weirdAverage(5)

(the tokens are: id lp num(which is expr) rp)

I get:

 Syntax error in line 1 '('

So, I try to remove this:

 precedence left ID;

And now I get an error:

   [java] Warning : *** Shift/Reduce conflict found in state #16
 [java]   between Expr ::= ID (*) 
 [java]   and     Call ::= ID (*) LP ExprComma RP 
 [java]   under symbol LP
 [java]   Resolved in favor of shifting.
 [java] Warning : *** Shift/Reduce conflict found in state #79
 [java]   between Expr ::= ID (*) 
 [java]   and     Call ::= ID (*) LP ExprComma RP 
 [java]   under symbol LP
 [java]   Resolved in favor of shifting.
 [java] Error : *** More conflicts encountered than expected -- parser generation aborted