compile-time error in "stringfwd.h" with all programs

[ath2441]

Whenever I attempt to compile any program with "#include <iostream>", the compiler gives a long string of errors, beginning with
iosfwd:41:0 and then many errors in stringfwd.h.
I was not having this error when I first began writing programs in C++. I did not write stringfwd.h, and the only explanation I can think of is that stringfwd.h somehow became corrupted. If so, how can I restitute the correct code for stringfwd.h so that my C++ programs compile.
I am using JGrasp for IDE and Windows 7 OS.
I corrected the error by downloading stringfwd.h from the Internet.