Yes, because of Themida. Themida is anti-debugger system protection form decompiling. You have to know reverse engineering very well to be able to unpack and crack this stuff. Anyway, Themida prevents any debugger from accessing to program's code. However, there is another problem. The DEX has itself protection from hacking, if you try to enter to dex server with l2phx (for example) the dex server won't allow you to go in, what is more he remembers that you tried some illegal stuff (on your PC) and disallows you to login to dex server anymore. However you don't have banned ip/acc and you can log in normally after "/format C:". The most interesting thing is that, the Dex does not use nophx.dll and does not import any other dll's to L2's executable file. So the 2nd and the 3rd method from this topic: http://www.maxcheaters.com/forum/index.php?topic=69323.0 won't work. However, I could not try the 1st one because when (I'm using latest version of PHX ~3.5 or something) I log into dex account the PHX doesn't show anything (as if I wasn't running L2), so I can't click this "floppy" button. Here's the problem.
Regards
EDIT: I have successfully changed my HDD ID and I still see "Access failed...". What's wrong?