[GiNaC-list] Strange behaviour in symbol declaration

Hy guys, I am doing a very long program (divided in diferent archives) that make some simplifications in indexed expressions. But if a declare a symbol variable completelly diferent in part of my program symbol x1("xi"); never used before, (yes, I checked if I declared this variable in main(), in other context..) this make diference im my output. In all functions declared in headers I am passing the simplified things as argument, so I think it not a symbol internal problem, like described in tutorial. My question: somebody got this behaviour before? if yes, what was resolved? Thanks for all Marco