"Dunno why no one gives the right advice. Stefan, if you read the data sheet, and the ports section in particular, it says that writing binary 1 to a port pin configures it as an input"

You should take your own advice Aman. and read the datasheet. Only Port 0 can "float", usually.

"As inputs, Port 1 pins that are externally pulled low will source
current because of the internal pull-ups." .. Mr. Datasheet.

As Mr. Datasheet says they are pull-ups, they are not floating are they ?

And P.S. Actually floating the 8052 pins to non logic-0 and logic-1 is not going to be that nice to a CMOS device!

More great datasheet reading:
"Maximum I OL per port pin: 10 mA
Maximum I OL per 8-bit port:
Port 0: 26 mA
Ports 1, 2 and 3: 15 mA
Maximum total I OL for all output pins: 71 mA
If I OL exceeds the test condition, V OL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions."... for a particular 8052

Can you guarantee the device being programmed is not defective, and won't exceed these ?