Just to tell you that it’s back working again. I don’t know for sure what made it work, since I’ve done so many things (I was desperate).
Anyway, this list of actions I took may help future users with problems:
1 – Disabled all plugins (didn’t seem to work). Then reenabled them.
2 – Reset permalink structure to default (didn’t seem to work). Turned it back to custom.
3 – Cleared all blank lines in ALL theme files (not just the ones before and after <php and ?>
4 – Deleted .htaccess (it was rebuild automatically later
This is all I can remember, but I may have done something else.
Hope it helps.