I'm unable to tell you the best way to proceed, because I've not much experience with foreign language / character set issues.
HOWEVER, I have discovered the actual problem. Actually, it was you that has discovered it with this latest observation, which has confirmed my earlier suspicion that it it is a character encoding issue.
The 'Category' is a 'red herring'. It doesn't have anything to do with the problem. The actual cause being related to the *existing products* in this category
This observation also suggests that looking for the fault in the language files themselves probably isn't going to help. That isn't where the problem is. You can/should revert the files back to the original hungarian.
Now we know what the problem *isn't*, we can concentrate more on what it *is*.
At some time or other you've managed to create a mismatch with your character sets. The original entries were made with one type of character encoding, and the new addition has been added/created with another.
This is evident if you look at the description of your newly added product (hungarian) and you'll see a couple of characters that look like "�". This is telling me that something isn't being decoded correctly. None of the original entries appear to have this problem, which suggests the encoding has been been changed at some stage.
Thinking about this logically, I would be expecting those original entries (without the apparent encoding issue) would be OK, and that it would be the new entry (with the "�" that *should* be having the problem. I have no explanation as why you are getting the effect opposite to what I'd expect, but nonetheless, that does appear to be the case.
So, whats the best way to go from here? Firstly, I'd wait a day or so to see if anyone else picks up on this thread and can offer step-by-step guidance.
If this isn't forthcoming, firstly you should read this:
http://www.zen-cart.com/content.php?...8859-1-to-utf8
Also read whatever else you can find on this subject (UTF8 vs iso-xxxx encodings) to ensure that you will be using the correct encoding for the hungarian language, which hopefully isn't going to cause you problems with the English & German languages. To do this correctly you'll need up update your SQL database tables (probably) as well as the 'defines' for the DB set in your configure.php files (and possibly elsewhere). You may only need to update one or the other. As I say, my experience here is really lacking, which is why I'm hoping someone with more experience will be of better help.
Anyway, after you've fixed this character set/encoding mismatch/problem, and since you don't have all that many products in your store anyway, rather than try to 'convert' the existing product data to bring everything back to the same/common format, it may be quicker and easier to just delete the products and re-enter them. Again, someone with more experience may be able to offer a better/easier/quicker solution
Cheers
Rod