Problem with braces in C

[Burkhard Schultheis]

We have overtaken a C program package with a horrible huge C function in 
it (about 3500 lines of code in a single function!). Now Emacs 21.3.1 
shows unbalanced braces at the first 5 opening braces. But:

1.) The code compiles without problems
2.) We can jump with match-paren to the corresponding closing braces
3.) A double-click with the left mouse button jumps to the corresponding 
braces, too.
4.) indent-region indents perfectly the whole function.

Is it a known bug?

Thank you in advance!

Regards
Burkhard