Why _Rclose fails

Good morning folks,

Can anyone give me an advise, why _Rclose can fail?
I'll try to describe the situation. There is a pretty complicated program, that 
must calculate a  long sequence of strutures. Normally it takes several 
iterations to get a "good" sequence. I used a PF in QTEMP to temporarily keep 
the sequence - seemed convinient...
When program completes a sequence calculation, it knows, if it is "good" or 
"not good". If it is "not good", it must be dropped. I failed to find a good 
way to flush a content of a PF, so decided to use _Rclose + _Ropen.

Here's what I have:

char FileName[24] ;

int main()
{
.....
  fpr = _Ropen(FileName, "wr") ;
.....
  Result = CallIterate(fpr) ;
.....
  Result = CallIterate(fpr) ;
.....
  _Rclose(fpr) ;
}

int CallIterate(_RFILE *fpr)
{
....
  _Rclose(fpr) ;
  fpr = _Ropen(FileName, "wr") ;
....
   return(0) ;
}

Program successfully makes first call to function CallIterate. When the second 
call is done, _Rclose fails with errno 3004 and generates exception CPF3130 - 
Member already in use.
And errno value is very content rich. It says - Guess what? - file has not been 
opened!

Can someone explain me what's happening and where to look for a solution?

Jevgeni Astanovski