Hi,
PSEN is an output when reset is inactive, and it shouldn't be grounded during power on, according to the data sheet.

Indeed and it is why I have said about switch. It is simple: in my sheme the PSEN is that signal which controls power-up process:
- if it is tied to groud then the bootloader starts;
- if it is leaved alone unconnected then the main program executes.

Another thing I have to say:
AT89C51RD2 has 64kb of program memory inside. So as long as you execute program from internal flash so PSEN will never be activated. It is the reason why I just unconnect it while program executes.

Regars,
Oleg