Just to confirm this for the final conclusion, you had a 22nF capacitor in place of C1/C2?
It would make perfect sense. Those two capacitors are there to filter high frequency harmonics of the crystal’s 4 MHz. At a capacitance 1000x the required value, they probably attenuated the signal itself enough so that the PIC didn’t get a clock signal. Without a clock signal, the PIC doesn’t run.
Yep that was the case. Thanks for the explanation, it makes really sense. Now I’m going for the next leap. Programming in Excel 2010 VBA. Up to now the k8055.DLL was not found. But first I’ll do me homework. 
I think you have already downloaded and extracted the “K8055N software pack”:
velleman.eu/downloads/files/ … ev1206.zip
from: velleman.eu/support/download … 055n&type=
If you have 32-bit operating system, copy the DLL from the package’s folder \DLL_v5.0.0.0 to the \Windows\System32 folder .
If you have 64-bit operating system, copy the DLL to \Windows\SysWOW64 folder.
Then you can try to run the Excel demo in the package’s folder: \Examples\K8055NDemoExcel
Yes I did already. But it doesn’t work in Excel2010 (VBA7) on a 64 bit OS (Windows 7). First of all I need to add “PtrSafe” in all Declarations. Example:
Private Declare Function Version Lib "k8055d.dll" () As Long…Needs to be changed to…
Private Declare PtrSafe Function Version Lib "k8055d.dll" () As LongAnd then in some cases the datatype Long needs to be changed in LongPtr in case of an address (Long is too short for addressing on a 64 bit OS).
It works however on Excel 2003, but I need to get it working on Excel2010 and windows 7. That’s why I called it the second leap