I have noticed that on a few occasions that another user was using my nickname. I have changed my nickname since and now someone else has the some nickname.

nicknames aren't registered on the ed2k network and aren't part of the clients identification process.
don't worry it isn't a problem some users share the same nick (like the default one http://emule-project.net)

There are milions of users out there. Try using a nick that cannot be thought up accidentally. MiCaL is good - less chance of someone having the same combination of uppercase and lowercase; MiCaL3295 is better.

The actually nickname that I was using was "<# BillY HunT #>". I realise that there are thousands of users out there but I wonder how many would think to use the same nickname as that.

That is indeed suspicious. Make no difference - nicknames are not part of the identfication process as KuSh pointed out earlier, but someone seems to think it does.
Do you remember which client software that other guy was using?

The other person was using client software eMule v0.44d [OS v3.93 ppRC2].

Thanks for the report. We like to keep an eye on such fellows. Sometimes they 'progress' to trying something more adventurous.

This was happening to me about 2 weeks ago. I changed my nix several times, and the the same user would "copy" it within a few minutes...I started reading up on some of the "hash stealing" posts here in the forum, and although I wasn't sure what was going on, I was having a problem staying on a server for more than 20 minutes...this was going on for about 5 or so months ... when I saw the nix clone, I was wondering if my hash got stolen, so I did a new reinstall, creating a new user hash in the process....Immediately after I did the new reinstall, the cloner showed up for a few days, then disappeared, and a few more days later, my server problems went away, I suppose after I rebuilt my new credits.

The cloner was using emule v0.46a, from Argentina...I copied down his other info as listed for future reference....

Best thing to do would be to "patent" or "copyright" your Nick.
That way instead of complaining about how "not" original you weren't,
you can sue the pants off the person who's "copying" you.

I am using: Emule Plus v1.2d

I have people using my Nickname all the time. If I change my nickname the nick thiefs will also change later(no specific time). There must be a Mod out there that allows people to single you out and lock on to your ID.

I almost always have nick thiefs from Israel,
so I changed my nickname to: ">>> Israeli Nick Thief if not US flag". That doesn't seem to deter them.

Here's one for example:
He uses Emule Plus v1.2d
Userhash: EC39E660800EAB0A4D589688DE456F7A
IP Address: 77.126.111.238.4662
ID: 1300131822
Server IP: 213.251.156.216.4000

They just seem to waste Que slots because most times I consistantly loose que position
ie: "QR: 76 (+7)". Some of them do download files though.

What I can't figure out is why they cling on to me? I don't think I download near as much as others, and their scores don't look high either.

He is most definitely NOT using eMule Plus.

What is happening is that there are some MODs out there that have a setting to do this, namely:

1. They read your nick and identify themselves to you as having the same nick (kind of a copy/paste operation).

2. They read your client software and version and identify themselves to you as having the same client software and version (kind of a copy/paste operation).

These actions are not harmful by themselves, just a little irritating. Just ignore them as much as you can.

Also, it is not personal; they are doing this to every client they are connected to - showing each of those clients their own nick and client software and version. E.g. if one such client is connected to both you and me, to you he will appear as using your nick, while at the same time to me he will appear as if he is using my nick.

I gave up on letting it bother me, I just can't figure out how they single me out ?
Also, I find them no matter what type/topic of file I download.

They DON'T single you out. They show EVERYONE a mirror. If you look into a mirror, you see your own face. If I look into the same mirror, I'll see my face. If there are a thousand mirrors around you and you look into every single one of them, you'll see your face in every single one of them. The mirrors don't know you; they don't recognize you. They just show what's in front of them.

I haven't come across a real explanation until now.

Thanks for the answer !

I don't think you should worry about that, at least until they don't steal your real name...