So I've just taken 5 minutes to download the 89C55WD & 89C52 datasheets & open them side-by-side in Acrobat Reader; You need go no further than page 9 to spot two obvious differences between the two chips:

1. The 89C55WD has an AUXR register that controls ALE and watchdog operation; the 89C52 doesn't have this register. Therefore, if your code messes this up it will affect an 89C55WD but not an 89C52.

2. The 89C55WD has two DPTRs, and a DPS bit in AUXR1 to choose between them; the 89C52 has none of these. Therefore, again, if your code messes these up it will affect an 89C55WD but not an 89C52.

Need I go on?