DRAWTEXT STRANGE PROBLEM PLEASE HELP

I am using follow drawtext function :

gc.DrawText(iMainMessage,rectTextMain,(rectTextMain.Height()+iHFont)/2,CGraphicsContext::ECenter,0);

iMainMessage is a TBuf<100>

now if I fill iMainMessage with iMainMessage.Append(_L("Hello")); it work but if I fill buffer from TBuf8 follow mode:

iMainMessage.Copy(iRecvBuf); where iRecvBuf is a TBuf8, I can see a rectangle for each char. Seem that the chars are not valid, but is not true.
I checked in debug and the iMainMessage data are correct, also I tried to show iMainMessage with CAknTextQueryDialog function and the text is showed correctly.

please help
thanks