I have exactly the same proplem. We did have ESET - so we un-installed it, but the issue (won't copy text to clipboard in Archicad) came back.
I've spent hours with very helpful ESET help desk trying to find the issue, and what happened was if we changed a settign on ESET , the 'copy text' issue goes away for a period (for an hour or a day ) only to turn up again.
I wonder if this is the same for other ESET uses - that it seemed like a fix initially to turn off 'Secure Browser Protection' in ESET, only for the problem to return.
I wonder if ESET is not actually the problem.
Can Archicad please comment on what they are doing to addess this? It is the only program I use that has a problem copying text to the clipboard. Pretty frustraiting.