I think une of this:
a) The rom is not programed
b) The rom is not well selected (CE, OE ...)

If you are reading, the pullups or pulldown are not important, the lines are fixed by the rom not by the 8052.
If you are reading high you can be sure that you don't need pullups because the pull-up puts high and you are retreiving high without it.
In my experience the external memory ever works well without pullups.

Regards.