Pull up resistor problem for Port 0

Hi all,
I am working on a project based on AT89C55. Here if i connect pull up resistor's of 10K to port '0',then it gives problem i.e. my controller get stuck up without giving any display on LCD. If i disconnect pull up, it works properly, giving always low on port 0 pins.[even i write FF to port 0 through program ].
I have tried with 1K pull up also,but nothing improvement. Also i need high-low transition on Port 0. I hv not connected any pull up to Port 1,2,3 as it has internal pull ups.


Plz.......... suggest

You need to connect the pull-up resistors of 10k to P0.
The controller wont get struck, please check the hardware.