Alright guys, I fixed this issue. Like I said before I'm not as knowledgeable about computers as you are, so please forgive me if I say something wrong 
.
The problem was with the file called "filter.wlx". I substituted this file in TCUP 4.2 with the one from TCUP 4.1 and everything is working fine now. Synchronizing "wlx" directories revealed that the following files were different:
1. fileinfo.wlx
2. positions.ini
3. mmedia.ini
4. filter.wlx
5. listfilter.ini
6. readme_details_eng.txt (not important in our case)
That's it, here my knowledge stops. I don't know why filter.wlx located in "PDFFilter" folder (which I would think has something to do with PDF documents format) ? was causing this problem.
Mmedia.ini has difference in line 19 but swapping these files (which I did first) didn't help. Also "fileinfo.wlx" in TCUP 4.2 indicates a newer version 2.0.10.0 comparing to TCUP 4.1 with 2.0.7.0 and has a little difference in dll dependency (is it important here?).
Well, I don't know where to go with all this but I have both "wlx" folders copied so if you need any of those files for your analisys please let me know.
.The problem was with the file called "filter.wlx". I substituted this file in TCUP 4.2 with the one from TCUP 4.1 and everything is working fine now. Synchronizing "wlx" directories revealed that the following files were different:
1. fileinfo.wlx
2. positions.ini
3. mmedia.ini
4. filter.wlx
5. listfilter.ini
6. readme_details_eng.txt (not important in our case)
That's it, here my knowledge stops
. I don't know why filter.wlx located in "PDFFilter" folder (which I would think has something to do with PDF documents format) ? was causing this problem. Mmedia.ini has difference in line 19 but swapping these files (which I did first) didn't help. Also "fileinfo.wlx" in TCUP 4.2 indicates a newer version 2.0.10.0 comparing to TCUP 4.1 with 2.0.7.0 and has a little difference in dll dependency (is it important here?).
Well, I don't know where to go with all this but I have both "wlx" folders copied so if you need any of those files for your analisys please let me know.