Elektor EPROM Emulator flaky

I constructed the EPROM Emulator published in Elektor magazine in the
SEPTEMBER 1992 issue. It worked quite well under Win98, but lately I
started using it on a HP Compaq nx9010 Pentium 4 laptop using WinXP,
and am getting inconsistent results. The downloading of code into the
target works successfully 1 out of 10 attempts. When the download
fails, the download LED flickers on and off. When the download was
successful, the LED stayed on continuously.

Any ideas? I tried changing the...

Elektor EPROM Emulator flaky