Rustu:
I have a similar problem. I have built an 8051 programmer that works fine with the AT89C51 and the 'original' AT89C55. A few days ago I tried to program an AT89C55 but I could'nt. Then I visited the Atmel's web site looking for information and I discovered that the magic letters 'wd' in the chip were very important: The programming method had changed. Some signals must be applied at different pins and, worst of all, the 5V supply must be raised to about 6 V.
I hope that Atmel continues to make the original chip. If not, I shall leave Atmel's MCUs and shall work with the Philips AT89C51RD+ for applications that require a flash memory of 20k or more.
By the way, will Atmel make a similar change with AT89C51 and AT89C52?.

Regards,
Alfredo del Río.