"Freemem" statement now gives "Invalid Pointer Operation". Used to work OK.

Hello Experts... I have a routine which would read a "chunk" of bytes from a file using a stream, do a bit of processing, then write that chunk to an output stream.. and repeat this till nothing left to read. Before the read I have these statements:

    Chunksize := 2048000;
    GetMem(CopyBuffer, ChunkSize); // CopyBuffer is defined as a PChar

And I do the read as such:

ibytesOK:=InfileStream.Read(CopyBuffer^, ChunkSize);

At the end when cleaning things up and closing files, I have this statement:

FreeMem(CopyBuffer, Chunksize);


This all used to work fine, until I just added some code that steps through the CopyBuffer a bit, looking for a #13 character:

while CopyBuffer^ <> #13 do  
       Inc(CopyBuffer);

Now when I run it, it crashes on the FreeMem(CopyBuffer, Chunksize); statement giving "Invalid Pointer Operation". Any idea how to remedy this, anyone?

Thanks!
    Shawn