It is Borland's C++ 5.5 fault if a proper call to seekg causes a crash, or your fault in case you are using it improperly. There's always the chance of other factors to be the reason for it, but less likely. One thing is for sure, though: the problem is not caused by Code::Blocks, and, therefore, you are asking in the wrong forums. It would be madness if we tried to provide support for each compiler, tool and library that you can use when working with Code::Blocks, as well as programming questions not related to the development of Code::Blocks itself.
I hope you can find the cause of your problem and a solution, but we are not to help you with it here. Maybe someone at StackOverflow can help you with it.