Hi Cepi,
yes I have 1.1.9.28 running with the older Whatsup 1.9 there was also no problem.
I also turned off the "Lauch Whatsup at startup" Option as mentioned before and several times disconnected and then closed the app before restarting still no contacts.

I now restarted the phone and I can see the list of contacts again.
BUT...in reverse Order... my list starts with Z entries..haha.. not really a problem but a bit uncomfortable and irritating if you don't expect it.