For 8051/52 usually we use, 10uf cap. from +5v to reset pin, and from reset pin 8.2k resistor to ground. Once I had the same problem, and used a 2.2k resistor inplace of 8.2k. It worked fine.

Even some time if you just use a good (working) 10uf electrolytic cap. from +5v to reset pin, it works fine, (I once tried without resistor to ground and it worked, I don't have idea how?)

Rauf /Microlink