I think my problem is solved!
Temp logger application is now running ok and no errors in programming.
I already programmed several 16F676's with no problem.
Problem was caused by combination of two things:
1. For some reason there was following lines in temp logger asm code:
org 0x03FF
goto init
These had to be removed from the code because this goto command overrides/conflicts with factory set RETLW command in location 3FF.
This RETLW returns factory set calibration value (in w-register) when application is CALLing it (as is done in this temp logger).
2. Velleman K8048 and progpic2 software tried to program this 3FF location (according to HEX-file) but I believe that
a bit more sophisticated programmers will not do this (even if told in HEX-file).
So these things together caused a lot of write failures (mostly in config word & eprom area).
If application is time sensitive (like this temp logger's RS-232 interface) the factory set calibration value must be used (moved to osccal-register).
Factory set calibration value can be read from blank chip using progpic2's readback-function. Calibration value can be seen in address 07FE. This should be 34xx where 34 is RETLW command and xx is calibration value which is used for correcting error of PIC's internal RC-oscillator.
The lucky one from Finland