gcc vs. egcs

[SeaTron]

hello,
 We are having a strange problem. We have a small c++ program that was
wrote by my freind,  He compiled it with egcs that came with his RH 6.2
and it works fine. But when he compiles it with gcc on his solaris, It works
but gives the wrong output. It is used to work vectors but he is not useing
math.h. 
Linux/egcs = works fine
Solaris/gcc = works fine but gives wrong outputs
No errors are given in compililation.
 Any ideas would be helpfull.
                               SeaTron