@Roger
My nuvi is always updated with the latest firmware, so that's not the issue. I've re-installed the latest firmware without a solution to my problem. I know that CNEUNT is better for 7x5 but I wanted to try this one, that's why I installed it. Thank You for the advices.

@Zakon
FYI - nüvi 765T reads 16 GB SD card. I've been using that card for a couple of years now. About so many img's - there is not enough space on the nuvi drive to have it all there and my 765 can't read >2GB files from SD card for some reasons, even though it has updated firmware. Plus I can then swap SD card from one nuvi to the other without probs.

@Neil
I know everything there is to know about naming and placing IMG's, so I have read those guides, but thank You for the links I'm not a newbie in this, You know. And as I said to @Roger, I loaded CNEUNTU in 765 with purpose of testing it to see how it works on it. If I brick it, that's me headache, not yours, but thank You for the warnings.

@Giomen
I hear You, but I'm very carefull with creating IMG's knowing of the issue with overlapping charts in different IMG's from the same distrubution (CNEUNT(U)), so there are none overlapping charts. And Yes, I've tried to see the real map, and there are just fine. I can even route from Denmark to Serbia without any problem. Even using address search.

@EVERYBODY
PROBLEM SOLVED
Thank You for all your help. Although none of Your advise worked for me. I solved this issue on my own. Problem was in the SD card and how the PC saw it. When it was in my nuvi and connected to the PC, SD card was recognised as FAT16 formatted. When I took the SD card out of the nuvi and put it directly in PC, it was recognised as FAT32. Then I put it back in nuvi, and it was recognised as RAW file system. I went then in computer administration and from there I formatted it as FAT32 with 4096b allocation sectors. now it's recognised as FAT32, no matter where I put it. After that, there were no problems with reading >2GB files from the SD card.

@mods/power users/admins
Don't threat everybody as a newbie just because of low amount of the posts. Be more respectfull and concetrate on being helpful, not correctional. We all live in the era of information and time is knowledge. Why should I read tons of useless information before I find the answer I need? Why couldn't I politely ask the question and You would politely answer to it for 1.000.000th time? Or anybody else for that matter. I know, that all of You are here to help, and I'm not picking on any of You particularly, but from reading the topics, I feel like some of You have forgotten that. And stop saying Google it, cause it's not perfect either and sometimes it doen't have answers although You search for something specific. Sorry I took your precious time, I wouldn't bother You any more with this issue.

PROBLEM SOLVED