strange error message in g++ 4.1.0 but not in 4.0.2

[KlausDGuenther]

In the following code:
______________________________________________
struct TSigRef : public DObject  {
   . . .
  friend void CDPTSigRef (PutGetFlag pgf, ASN1* cid, address varAddr,
                                       bool baseCDP=false);

  virtual void CDP (PutGetFlag pgf, ASN1* cid,
                            bool baseCDP=false)
/*line 56:*/  { CDPTSigRef(pgf,cid,(address)this,baseCDP); }
};
______________________________________________

g++ 4.1.0 reports:

Syntax.h:56: error: 'CDPTSigRef' was not declared in this scope

The error disappears if "address" (typedef void *address) is
replaced, for instance, with "TSigRef*" in both places where it
is used.

The problem didn't occur in g++ 4.0.2.

Could this be a bug in g++ 4.1.0?

Klaus.